Patent Publication Number: US-6699085-B2

Title: Engine power output control for small watercraft

Description:
PRIORITY INFORMATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 09/494,392, filed Jan. 31, 2000, now allowed, which claims priority to Japanese Patent Application No. 11-022,650, filed Jan. 29, 1999, the entire contents of which are both hereby expressly incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to an improved mechanism for controlling the speed of a personal watercraft. More particularly, the present invention relates to an improved throttle control system for a personal watercraft. 
     2. Description of Related Art 
     Personal watercraft are a relatively small sporty-type of watercraft wherein the rider sits or stands more on top of the watercraft than in other types of watercraft. Typically, a personal watercraft is designed to be operated by a single rider or operator, although accommodations are frequently made for one or more passengers. 
     Personal watercrafts are typically powered by an internal combustion engine. Fuel is supplied to the engine by charge formers, which can be carburetors or fuel injectors depending upon the application. Air is supplied to the engine by an air induction system. Located within the air induction system is one or more throttle valves that regulate the amount of air delivered to the engine. Because fuel flow is typically metered in proportion to the air flow, the throttle valves, in essence, control the power output of the engine and thus the speed of the watercraft as is well known in the art. 
     Personal watercraft typically include a handlebar that is mounted to an upper deck of the watercraft. The operator uses the handlebar to steer the watercraft. On the handlebars, near a grip, is a throttle lever. The throttle lever is typically directly coupled to the throttle valves by one or more cables. Accordingly, the operator controls the position of the throttle valves thereby the speed the watercraft by moving the throttle lever. 
     The throttle valves are normally biased to an idling position by one or more return springs. Another spring biases the throttle lever back to an unactuated position that corresponds to the idle position of the throttle valves. In order to further open the throttle valves and increase the speed of the watercraft, the operator typically grasps the throttle lever with one or more of her fingers and moves the lever towards the handlebar grip. When the operator releases the throttle lever, the return springs force the throttle valves and the throttle lever back to the idling position. Therefore, in order to maintain the speed of the watercraft, the operator must hold the throttle lever at a specific position against the return force of the return springs. Furthermore, if the operator&#39;s fingers slip, the throttle lever will return quickly to the idling position causing the watercraft to decelerate suddenly. 
     SUMMARY OF THE INVENTION 
     The prior art system for controlling the position of the throttle valves in a personal watercraft has several disadvantages. For example, to maintain the speed of the watercraft, the operator must hold the throttle lever against the force of the return springs. Accordingly, the operator&#39;s fingers may become tired after holding the throttle lever only for awhile. Another problem with the prior art system is that if the operator suddenly lets go of the throttle lever the throttle valves quickly return to their idling position causing the watercraft to decelerate quickly. This sudden deceleration can cause the watercraft to suddenly slip from a planing state to a non-planing state. 
     Accordingly, an aspect of at least one of the inventions disclosed herein involves a personal watercraft comprising a hull and an internal combustion engine disposed within the hull. The engine includes an air induction system that supplies air to the engine and has a throttle device to regulate the amount of air supplied to the engine. A steering mechanism steers the watercraft and includes a handlebar assembly coupled to the hull for this purpose. A throttle device control system includes a throttle operator that is located on the handlebar assembly and is arranged to be controlled by a rider of the watercraft. An operator position sensor is configured to detect the position of the throttle operator and to output a data signal that is indicative of the detected position of the throttle operator. A controller communicates with the operator position sensor to receive the data signal and is configured to output a control signal in response to the data signal. An actuator communicates with the controller. The actuator also is coupled to the throttle device and is adapted to adjust the throttle device in response to the control signal from the controller. 
     Another aspect of at least one of the inventions disclosed herein involves a personal watercraft comprising a hull and an internal combustion engine disposed within the hull. The engine includes an air induction system that supplies air to the engine and has a throttle device to regulate the amount of air supplied to the engine. A steering mechanism controls the steering movement of the watercraft and includes a handlebar assembly coupled to the hull. A throttle device control system includes a throttle operator that is located on the handlebar assembly and is arranged to be controlled by a rider of the watercraft. Means are provided for detecting a position of the throttle operator, and for moving said throttle device in response to the detected position of the throttle operator. Yet another aspect of the present invention involves a personal watercraft comprising a hull defining an engine compartment and an internal combustion engine disposed within the engine compartment. The engine includes an air induction system that supplies air to the engine and has a throttle device to regulate the amount of air supplied to the engine. A steering mechanism steers the watercraft and includes a handlebar assembly coupled to the hull for this purpose. A throttle device control system includes a throttle operator that is located on the handlebar assembly and is arranged to be controlled by a rider of the watercraft. An operator position sensor is mounted within the engine compartment and is configured to detect the position of the throttle operator and to output a data signal that is indicative of the detected position of the throttle operator. A controller communicates with the operator position sensor to receive the data signal and is configured to output a control signal in response to the data signal. An actuator mounted within the engine compartment communicates with the controller. The actuator also is coupled to the throttle device and is adapted to adjust the throttle device in response to the control signal from the controller. 
     A further aspect of at least one of the inventions disclosed herein involves a personal watercraft comprising a hull and an internal combustion engine disposed within the hull. The engine includes an air induction system that supplies air to the engine and has a throttle device to regulate the amount of air supplied to the engine. A steering mechanism controls the steering movement of the watercraft and includes a handlebar assembly coupled to the hull. A throttle device control system includes a throttle operator that is located on the handlebar assembly and is arranged to be controlled by a rider of the watercraft. Means are provided for detecting a position of the throttle operator, and for moving said throttle device in response to the detected position of the throttle operator. 
     Further aspects, features, and advantages of the inventions disclosed herein will become apparent from the detailed description of the preferred embodiments which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features, aspects and advantages of the present inventions now will be described with reference to the drawings of preferred embodiments of the inventions, which are intended to illustrate and not to limit the present inventions, and in which drawings: 
     FIG. 1 is a partially sectioned top view of a personal watercraft, which has a throttle valve control system configured in accordance with the present invention, with some of the watercraft components and features illustrated in phantom; 
     FIG. 2 is a partially sectioned side view of the watercraft illustrated in FIG. 1, with some internal components of an engine and jet pump illustrated in phantom; 
     FIG. 3 is a cross-sectional view of the watercraft illustrated in FIG. 1, taken along the line  3 — 3  in FIG. 2; 
     FIG. 4 is a cross-sectional view of a throttle lever and throttle lever position sensor that is configured in accordance with the present invention; 
     FIG. 5 is partially sectioned top view of the throttle lever and throttle lever position sensor illustrated in FIG. 4; and 
     FIG. 6 is a schematic diagram illustrating another embodiment of a throttle valve control system configured in accordance with the present invention. 
     FIG. 7 is a partially sectioned and top plan view of an embodiment of a throttle control relay assembly having a throttle lever position sensor and an actuator contained within a housing. 
     FIG. 8 is a partial cut-away view of the throttle lever position sensor of FIG.  7 . 
     FIG. 9 is a side elevational view of the throttle control relay assembly of FIG. 7 showing an output pulley of the actuator. 
     FIG. 10 is a partially sectioned view of another embodiment of a throttle lever position sensor. 
     FIG. 11 is a schematic representation of one embodiment of a throttle valve control system. 
     FIG. 12 is a partially sectioned side view of the watercraft illustrated in FIG. 1, with some internal components of an engine and jet pump illustrated, and showing another preferred location of a throttle lever position sensor of FIG.  10 . 
     FIG. 13 is a partial view of a throttle body assembly removed from a watercraft and illustrating one embodiment of a coupling between an actuator and the throttle valves. 
     FIG. 14 is a schematic representation a throttle valve control system in accordance with another embodiment. 
     FIG. 15 is another partial view of a throttle body assembly removed from a watercraft and illustrating another embodiment of a coupling between an actuator and the throttle valves. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention generally relates to an improved engine output control system for a personal watercraft. The engine output control system is described in conjunction a personal watercraft because this is an application for which the system has particular utility. Those of ordinary skill in the relevant arts will readily appreciate that the arrangements described herein also may have utility in a wide variety of other settings, including other types of watercraft and land vehicles. 
     With reference now to FIGS. 1 and 2, a personal watercraft, which is indicated generally by the reference numeral  20 , is illustrated therein. The watercraft  20  includes a hull  22  that is defined by a top portion or deck  24  and a lower portion  26 . These portions of the hull  22  are preferably formed from a suitable material such as, for example, a molded fiberglass reinforced resin. For instance, the hull lower portion  26  can be formed using a sheet molding compound (SMC), i.e., a mixed mass of reinforced fiber and thermal setting resin that is processed in a pressurized, closed mold. The molding process desirably is temperature controlled such that the mold is heated and cooled during the molding process. For this purpose, male and female portions of the mold can include fluid jackets through which steam and cooling water can be run to heat and cool the mold during the manufacturing process. 
     The lower hull portion  26  and the upper deck  24  are joined around the peripheral edge at a bond flange  28 . Thus, the bond flange  28  generally defines the intersection of the lower portion  26  of the hull  22  and the deck  24 . 
     As viewed in a direction from the bow to the stem of the watercraft  20 , the upper deck portion  24  includes a bow portion  30 , a control mast  32 , a front seat  34 , a rear seat  36  and a boarding platform  38 . The bow portion  30  preferably slopes upwardly toward the control mast  32 . A hatch cover  40  can be provided within the bow portion  30 . The hatch cover  40  preferably is pivotally attached to the upper deck  24  and is capable of being selectively locked in a closed and substantially watertight position. The hatch cover  40  covers a storage compartment  41 . 
     The control mast  32  extends upward from the bow portion  30  and supports a handlebar assembly  44 , which includes a handlebar and a pair of handlebar grips  198  that are mounted on the ends of the handlebar. The handlebar assembly  44  controls the steering of the watercraft  20  in a conventional manner. The handle bar assembly  44  also carries a variety of the controls of the watercraft, such as, for example, a start switch and a lanyard switch. Additionally, an engine output request device, such as, for example, but without limitation, a throttle lever  200 , described in greater detail below, can be positioned on the handlebar next to one of the grips  198 . 
     With continued reference to FIGS. 1 and 2, the upper deck  24  further comprises a longitudinally extending seat pedestal  48 . In the illustrated arrangement, the pedestal  48  supports the front seat  34  and the rear seat  36 . The front  34  and rear seats  36  are desirably of the straddle-type. A straddle-type seat is well known as a longitudinally extending seat configured such that operators and passengers sit on the seat with a leg positioned to either side of the seat. Thus, an operator and at least one passenger can sit in tandem on the seats  34 ,  36 . Of course, the two seats  34 ,  36  can be combined in some arrangements into a single seat mounted to the raised pedestal  48 . Moreover, these seats  34 ,  36  are preferably centrally located between the sides of the hull  22 . 
     As illustrated in FIGS. 1 and 3, foot areas  56  are formed alongside the pedestal  48  and are generally defined as the lower area located between the pedestal  48  and a pair of raised side gunwales or bulwarks  58  that extend along the outer sides of the watercraft  20 . The foot areas  56  preferably are sized and configured to accommodate the lower legs and feet of the riders who straddle the seats  34 ,  36 . As described above, the illustrated watercraft  20  also includes the boarding platform  38  that is connected to the illustrated foot areas  56  and that is formed at the rear of the watercraft  20  behind the pedestal  48 . The boarding platform  38  allows ease of entry onto the watercraft  20 . 
     With reference back to FIGS. 1 and 2, the front seat  34  covers an access opening  50  that allows access into a cavity  52  defined by the hull  22 . The cavity  52  formed between the two hull sections  24 ,  26  is divided by one or more bulkheads. In the illustrated watercraft  20 , a bulkhead  54  preferably is disposed within the hull cavity  52  to divide the cavity  52  into an engine compartment  60  and a pump compartment  61 . As will be described, air ducts extend into the cavity to ventilate the cavity and to cool various components of the watercraft. 
     As described above, the access opening  50  is formed on a top surface of the pedestal  48  and is desirably positioned beneath at least one of the seats  34 ,  36 . Thus, the access opening  50 , or maintenance opening, is covered by the seat  34  in a water-sealing manner. For this purpose, one or more seals  66 , or gaskets, can circumscribe the opening  50 . 
     The rear seat  36  in the illustrated embodiment covers the an electronic control unit (ECU)  113 . The ECU is supported and protected by a platform  53 , which is supported within the hull  22  by the bulkhead  54 . The platform  53  also forms a storage compartment  51  that is also covered by the rear seat  36 . 
     An engine  68  is mounted within the cavity  52  of the illustrated watercraft  20  using resilient mounts  69  as is well known to those of ordinary skill in the art. Although the engine  68  may be of any known type, in the illustrated embodiment and in the preferred form, the engine  68  is of the four-cycle, overhead valve type. It should be appreciated that while the illustrated engine  68  is of the four-cycle variety, the engine  68  can also be of the two-cycle, diesel, or rotary variety as well. 
     The general construction of a four-cycle, overhead valve type engine is well known to those of ordinary skill in the art. As illustrated in FIGS. 1 through 3, the engine  68  generally comprises a cylinder block  70 , a cylinder head  72 , a cylinder head cover  74 , and a crankcase  76 . Four in-line cylinders  78   a-d  are formed within the cylinder block  70 . However, the engine  68  can have one, two or more than three cylinders and can be inclined, opposed or formed with two banks of cylinders. 
     The cylinders  78  are capped by the cylinder head  72  and cylinder head cover  74 . A piston  81  is reciprocally mounted within each of the cylinders  78   a-d  and a combustion chamber  79  is defined within the cylinder  78  by the top of the piston  81 , the wall of the cylinder and a recess formed within a lower surface of the cylinder head  72 . 
     The cylinder head  72  journals a pair of overhead camshafts  180  that directly actuate the intake and exhaust valves  182 ,  184  for opening and closing the intake and exhaust passages  186 ,  188 . The camshafts  180  are covered by a cam cover  181 . The intake valves  182  permit the flow of an intake charge into the combustion chambers  79  of the engine from an induction system  102  that is disposed at one side of the cylinder head. The induction system  102  is described in more detail below. As is well-known in the art, the exhaust valves  184  govern the flow of exhaust from the combustion chamber  79 . 
     The crankcase  76  is attached to the opposite end of the cylinder block  70  from the cylinder head  72 . A crankcase chamber  80  generally is defined by the crankcase  76  and the cylinder block  70 . A crankshaft  82  is positioned within the crankcase  80  and is connected to the pistons  81  through a set of connecting rods. As the pistons  81  reciprocate within the cylinders  78 , the crankshaft  82  is rotated within the crankcase chamber  80 . 
     As shown in FIGS. 1 and 2, the crankshaft  82  preferably is in driving relation with a jet propulsion unit  84  that is provided in the pump chamber  62 . The pump chamber  62  is formed in part by the hull  22  and a bottom plate  91  that protects the lower side of the jet propulsion unit  84 . The jet propulsion unit  84  preferably includes an impeller shaft  86  to which a propeller or an impeller  88  is attached. The crankshaft  82  and the impeller shaft  86  desirably are connected through a conventional shock-absorbing or resilient coupling  90 . The impeller shaft  86  extends in the longitudinal direction through a propulsion duct  92 , that can be defined by the lower portion of the hull  26 . The propulsion duct  92  has a water inlet  94  positioned on a lower surface of the hull  22 . The lower portion  26  of the hull  22  also includes an opening  96  in the stern of the watercraft in which a jet outlet port  98  of the propulsion unit  84  is positioned. The propulsion unit  84  generates the propulsive force by applying pressure to water drawn up from the water inlet port  94  by rotating the impeller shaft  86  and by forcing the pressurized water through the jet outlet port  98  in a manner well known to those of ordinary skill in the art. 
     A nozzle deflector  100  or steering nozzle is connected to the discharge nozzle  98  of the propulsion unit  84 . The nozzle deflector  100  desirably moves in the left/right and vertical directions via a well known gimbal mechanism. The nozzle deflector  100  is connected to the handlebar assembly  44  through a steering mechanism and a trim mechanism (not shown), whereby the steering and trim angles can be changed by the operation of the handlebar assembly  44  and the associated trim controls. 
     As illustrated in FIG. 3, the engine  68  also includes an induction system  102  that is configured to guide air toward the engine  68  for combustion in each combustion chamber  80 . Preferably, the air intake system includes an intake box  104  or silencer into which air from within the engine compartment  60  is drawn through an air induction inlet  105 . The air is then delivered to the charge formers  110 , described below. 
     With reference to FIG. 2, the watercraft  20  also includes a fuel system which includes a fuel tank  42  positioned within the cavity  52 . An operator fills the fuel tank  42  through the fuel fill port  43 . Conventional means, such as straps (not shown) secure the fuel tank  42  in position along the lower hull portion  26 . The fuel is supplied from the fuel tank  42  to the charge former  110  through any suitable fuel pumping arrangement. The charge formers  110  can be carburetors or fuel injectors depending upon the application. The arrangement illustrated in FIG. 2, however, is carbureted. 
     The carburetors  10  vaporize and mix fuel with the intake air to form an intake charge. A throttle device  112  regulates the air flow through the induction system. In the illustrated embodiment the throttle device is a plurality of butterfly valves  112  that are located in the carburetors  110 . However, one of ordinary skill in the art will understand that other types of throttle devices  112  may be used. The throttle device  112  is preferably controlled by a throttle control system in a manner that will be described in greater detail below. Ultimately, the intake charge is delivered to the combustion chamber  79  through the intake passages  186  that are formed in the cylinder head  72 . 
     A suitable ignition system is provided for igniting the air and fuel mixture in each combustion chamber  79 . Preferably, this system comprises a spark plug  114  corresponding to each cylinder  78 . The spark plugs  114  are preferably fired by a suitable ignition system that is controlled by the ECU  113  as is well known to those of skill in the art. The ECU  113  is connected to the spark plugs by one or more cables  111 . 
     Exhaust gas generated by the engine  68  is routed from the engine  68  to a point external to the watercraft  20  by an exhaust system  115  which includes the exhaust passages  188  leading from each combustion chamber  79  through the cylinder head  72 . An exhaust manifold  116  or pipe is connected to a side of the engine  68 . As best illustrated in FIG. 3, the exhaust manifold  116  is connected to one side of the engine  68  while the intake system of the engine  68  is connected to the opposite side of the engine  68 . 
     The manifold  116  has a set of branches  118  each having a passage that corresponds to one of the exhaust passages  188  leading from the combustion chambers  79 . The branches  118  of the manifold  116  merge at a merge pipe portion  120  of the manifold  116 , which extends in a generally forward direction. The merge pipe portion  120  has a further passage through which the exhaust is routed. 
     An expansion chamber  122 , which lies behind the engine  68  on the same side as the exhaust manifold  116 , is connected to the exhaust manifold  116 , preferably via a flexible member  123  such as a rubber hose. The expansion chamber  122  has an enlarged passage or chamber through which exhaust flows from the passage in the exhaust manifold  116 . A catalyst (not shown) may be positioned within the expansion chamber  122 . 
     After flowing through the expansion chamber  122 , the exhaust gases flow to a water lock  130 , which is located on the opposite side of the watercraft  20 . The expansion chamber  122  is preferably connected to the water lock  130  via a flexible hose  131 . The exhaust gases flows through the water lock  130 , which is preferably arranged in a manner well known to those of ordinary skill in the art, to prevent the backflow of water through the exhaust system to the engine  68 . The exhaust gases then pass through a water trap  132 , which extends over the pump chamber  62  to the other side of the watercraft  20 . The water trap  132  has its terminus on a side of the pump chamber  62 . 
     As shown in FIGS. 1 and 2, most of the expansion chamber  122  and the entire water lock  13  are located in the pump compartment  61 , which is formed in part by the bulkhead  54  and lies behind the engine compartment  60 . Because of the exhaust gases, the expansion chamber  122  and the water lock  120  are relatively hot. An advantage of the illustrated watercraft  20  is that these hot components are separated from the engine by the bulkhead  54 . The platform  53 , which is located above the pump compartment  61  also isolates the ECU from these hot components. Another advantage of the illustrated watercraft  20  is that the both the flexible hose  130  and the water trap  132  extend up and across the watercraft  20  and over (i.e., at a vertical position higher than) the pump chamber  62 . This configuration prevents water that has entered the exhaust system from reaching the engine  68 , especially when the watercraft  20  is capsized. 
     The engine  68  includes a suitable lubricating system for providing lubricant to the various moving parts of the engine Specifically, an lubrication supply tank  134  is provided on a side of the engine  68  opposite the exhaust system  115  and below the induction system  102 . The lubricant tank  134  is filled through the lubricant filler port  127  that extends from the top of the tank  134 . A supply hose  135  connects the supply tank  124  to a supply pump  136 . The supply pump  136  delivers lubricant to circulating passages  138  within the engine  68 . A lubrication filter  139  is preferably inserted into the lubrication path to clean the lubricant as is well known in the art. A lubrication pan  137  that is located at the bottom of the crankcase  76  collects the used lubricant. A scavenge pump  133  returns lubricant in the lubrication pan  137  to the supply tank  134 . The scavenge pump  133  is connected to the lubrication tank by a return hose  129 . 
     The engine  68  can also include a suitable liquid and/or air cooling system. Moreover, the watercraft  20  can include a bilge system for drawing water from within the hull cavity  52  and discharging it into the body of water. These systems are well known in the art and their description is not necessary for an understanding of the present throttle control system. 
     Preferably, air is drawn into the engine compartment  60  through several air ducts. As illustrated, a forward air duct  140  is positioned in front of the engine  68  near the front end of the watercraft  20 , and an aft air duct  142  is positioned behind the engine  68  towards the stem of the watercraft  20 . As will be recognized, the number of ducts  140 ,  142  is not critical and can be varied as desired depending upon the application. Due to the strategic locations of the forward duct  140  and the aft duct  142  in general, an air current can be set up within the engine compartment  60  to induce a flow of air across at least a portion of the engine  68 ; however, such a cross-current need not be used to cool the engine. 
     The personal watercraft so far described is conventional and represents only an exemplary personal watercraft on which the present throttle control system can be employed. Therefore, a further description of the personal watercraft is not believed necessary for an understanding and appreciation of the present invention. 
     The engine output control system will now be described with reference to FIGS. 1,  2 ,  3 ,  4 , and  5 . The engine output control system comprises the throttle lever  200 , a throttle lever position sensor  202 , and a throttle valve actuator  204 . In the illustrated embodiment, as shown in FIG. 1, the throttle lever  200  is positioned on the handlebar assembly  44  near the right grip  198 . The throttle lever  200  can, however comprise other types of operators, such as, for example, but without limitation, a thumb trigger, a push button, a twist grip, a pedal or the like. The throttle operator also can be located else where on the watercraft  20  and/or assume a variety of orientations on the watercraft in order to ease operations. For instance, in the illustrated embodiment, the throttle lever  200  is arranged to rotate about an axis that lies generally normal to an axis of the portion of the handlebar assembly  44  to which it is attached and/or to an axis of the hand grip  198 . The throttle lever in some forms can be arranged to move parallel relative to or obliquely with respect to, or about the axis of the portion of the handlebar assembly  44  to which it is attached and/or to an axis of the hand grip  198 , e.g., rotation about an axis that coincides with the axis of the hand grip  198 , as in the case of a twist grip. In any of these embodiments, the lever  200  provides a manually operable input device for allowing an operator of the watercraft  20  to issue a power output request, i.e., the position to where the lever  200  is moved corresponds to a power output desired by the operator. Thus, when the operator wishes more power output from the engine  68 , the operator can squeeze and thereby further deflect the lever  200 . 
     In the illustrated embodiment, the throttle lever position sensor  202  is also located on the handlebar assembly  44  near the right grip  198 ; however, it could also be located elsewhere on the watercraft. In one variation, for instance, the throttle lever position sensor  202  can be located within the hull and be coupled to the throttle lever  200  by an interposed mechanism. 
     The throttle valve actuator  204  preferably is located within the cavity  52  of the hull  22 . As will be described in detail below, the throttle lever position sensor  202  indicates the position of the throttle lever  200  to the throttle valve actuator  204 . The throttle valve actuator  204  opens and closes the throttle valves  112  in response. Accordingly, the throttle lever  200  indirectly controls the position of the throttle valves  112 . 
     With reference to FIGS. 4 and 5, the throttle lever  200  includes an elongated shaft  206  that is suitably journaled for rotation within a case  208 . The case  208  preferably is substantially waterproof and preferably made of a resin based material. A nut  210  is attached to a threaded portion  212  of the shaft  206  and prevents the throttle lever  200  from being lifted out of the case  208 . One or more seals  212  surround the shaft  206  and prevent water from entering the case  208 . 
     With reference to FIG. 4, an internal wall  214  divides the case  208  into an upper chamber  216  and a lower chamber  218 . The upper chamber houses a torsional spring  220  that is attached to the elongated shaft  206 . The spring  220  biases the throttle lever  200  to the traditional idling position, which is indicated by line I of FIG.  5 . The lower chamber  218  houses the throttle lever position sensor  202 , which will be described in detail below. 
     As shown in FIG. 1, the case  208  is mounted to a fixture  222  that is attached to the handlebar assembly  44  next to the right hand grip  198 . As best seen in FIG. 5, the fixture  222 , the case  208 , and the throttle lever  200  are arranged such that the operator can grasp the handlebar grip  198  and actuate the throttle lever  200  with her index finger  224 . By squeezing her index finger  224 , the operator can rotate the throttle lever  200  from the idling position to the full throttle position (indicated by line FT of FIG.  5 ). When the operator releases the throttle lever  200 , the spring  220  returns the throttle lever  200  to the idling position. 
     With reference back to FIGS. 4 and 5, the throttle lever position sensor  202  is formed within the lower chamber  218 . In the illustrated arrangement, the components of the throttle lever position sensor  202  form a rheostat. A rheostat is a current-setting device in which one terminal is connected to a resistive element and the second terminal is connected to a movable contact to place a selective section of the restive element into the circuit. The current set by the rheostat comprises the signal indicating the position of the throttle lever  200 . It should be appreciated that other circuits could be used in the throttle lever position sensor  202 , such as, for example, a potentiometer. In such a system, the voltage set by the potentiometer would indicate the position of the throttle lever  200 . However, the illustrated throttle lever position sensor  202  is preferred because it uses a small number of parts and is particularly suited for rugged use. 
     The components of the illustrated arrangement of the throttle lever position sensor  202  will now be described. In the lower chamber  218 , a movable contact  228  is attached to an arm  230 . The arm  230  includes annular sleeve  231  that includes slots (not shown). The sleeve  231  fits over splines  232  formed on the lower end of the elongated shaft  206 . A C-ring  231  secures the sleeve  231  at an axial position along the elongated shaft  206 . Because the arm  230  and the elongated shaft  206  are coupled together, the movable contact  228  rotates with the throttle lever  200 . 
     The moveable contact  228  is made of conductive material, such as, for example, copper. The moveable contact  228  includes a first contact point  234  and a second contact point  236 . The first contact point  234  contacts a resistive element  238 , which is attached to a lower surface  233  of the lower chamber  218 . The resistive element  238  can be manufacture as, for example, a carbon composition film, a metallic film, or a wire-wound resistor. As shown in FIG. 5, the resistive element  238  is arc-shaped. Accordingly, as the throttle lever  200  is rotated, the first contact point  234  remains in contact with the resistive element  238 . 
     The second contact point  236  of the moveable contact  228  contacts a stationary contact  240  that is mounted to a side wall  237  of the case  208 . The side wall  237  and the stationary contact  240  are also arc-shaped such that as the throttle lever  200  rotates the second contact  236  stays in contact with the stationary contact  240 . The stationary contact  240  is also made of a conductive material such, for example, copper. 
     A first electric wire  242  is connected the resistive element  238 . Similarly, a second electric wire  244  is connected the stationary contact  240 . Both wires  242 ,  244  are protected by a casing  243 . The wires  242 ,  244  are routed through the watercraft  20  and are connected to the ECU  113 . A closed circuit consisting of the ECU  113 , the first wire  242 , the resistive element  238 , the moveable contact  228 , the stationary contact  240 , and the second wire  244  is formed. The ECU  113  supplies a voltage to the circuit. 
     The current i in the circuit indicates the position of the throttle lever  200  as will be explained below. When the throttle lever  200  is in the idling position, a large portion of the resistive element  238  is placed into the circuit. Accordingly, the circuit has relatively large total resistance R I . Consequently, for a given voltage, the current i I  flowing through the circuit will be relatively small according to the equation V=iR. 
     In comparison, when the throttle lever  200  is in the full-throttle position, a smaller portion of the resistive element  238  is placed into the circuit. Accordingly, the total resistance R FT  of the circuit is less than the total resistance R I  of the circuit in the idling position. Consequently, the current i FT  flowing through the circuit is larger than the current i I  flowing through the circuit in the idling position. Thus, for a given voltage the current i indicates the position of the throttle lever  200  in accordance with the linear relationship between i and R. The ECU  113  senses the current and determines the position of the throttle lever. 
     A wire  254  connects the ECU  113  to the valve actuator  204 , which is located in the engine cavity  60  in front of the engine  68  (FIG.  1 ). The valve actuator  204  comprises a prime mover (not shown), such as, for example, a stepper motor or a servo motor. The actuator also includes a pulley  250 . Bowden-wire cables  252  are coupled to the pulley  250  and the throttle valves  112  such that rotation of the pulley  250  causes the throttle valves  112  to open and close. The throttle valve actuator  204  opens and closes the throttle valves  112  in response to a signal generated by the ECU  113 . 
     When the throttle lever  200  is in the idling position, the current i in the circuit is relatively small as explained above. The ECU  113  senses the small current and sends a signal to the actuator  204  to adjust the throttle valves  112  to the idling position. As the throttle lever  200  is moved towards the full throttle position, the current i in the circuit increases. In response, the ECU  113  sends a signal to the actuator  204  to open the throttle valves  112 . In this manner, the throttle lever  200  indirectly controls the position of the throttle valves  112 . 
     As shown in FIG. 1, a meter  256  is connected to the circuit by a wire  258 ; alternatively, the meter  256  is connected to the ECU  113 . The meter  256  is mounted onto the control mast  46  and indicates the position of the throttle lever  200  according either the current in the circuit or a signal generated by the ECU  113  in response to the current in the circuit. 
     From the above description, it is readily apparent that the illustrated power output control system has several advantages as compared to prior art control systems. For example, prior art throttle valves are normally biased to an idling position by return springs. These return springs generally are relatively stiff in order to overcome the force of air flow across the throttle valve. The prior art throttle levers are typically directly coupled to the throttle valve. Accordingly, the operator must hold the throttle lever against the force of the return springs in order to maintain a specific speed. In comparison, the throttle lever  200  in the illustrated throttle control system indirectly controls the throttle valves  112 . That is, the actuator  204  opens and closes the throttle valves in response to the detected position of the throttle lever  200 . The return spring  220  returns the throttle lever  200  to the idling position. Accordingly, the return spring  220  can be designed to be significantly weaker than the throttle valve return springs of the prior art. Accordingly, the throttle lever  200  has a “light touch” and the operator&#39;s fingers becomes less tired after holding the throttle lever  200  for a long period of time. 
     FIG. 6 is a schematic illustration of another arrangement of a throttle valve control system according to the present invention. The control system includes a throttle lever  200 , a throttle lever position sensor  202 , and an actuator  204 . These components are arranged essentially as described above. The throttle lever position sensor  202  determines the position of the throttle lever  200 . The throttle valve actuator  204  opens and closes the throttle valves  112  in response to the detected position of the throttle lever  200 . Accordingly, the throttle lever  200  indirectly controls the position of the throttle valves  112 . 
     The throttle lever  200  is also configured to directly adjust the throttle valves  112 . As shown in FIG. 6, the throttle lever  200  is connected by a means such as a Bowden-wire cable  262  to a lost motion device  264 . A wide variety of lost motions devices, which are well known in the art, can be used in accordance with the present invention. Lost motion devices are typically inserted between two elements whereby the motion of one element is to be partially transferred to the other. The lost motion device absorbs the motion of the first element for a range of motion and transfers motion to the second element for another range of motion. For example, a spring can be inserted between two elements. The spring absorbs motion the motion of the first element until the spring is completely compressed. Once compressed, the motion of the first element is transferred to the second element. As shown in FIG. 6, the illustrated lost motion device  264  is connected to the throttle valves  112  by a means such as a Bowden-wire cable  262 . 
     Desirably, the lost motion device  264  absorbs the motion of the Bowden-wire cable  262  when the throttle lever  200  is moved from the idling position to a planing speed position. Accordingly, the throttle lever  200  does not directly open the throttle valves  112  until the watercraft  20  reaches a planing state. Instead, the throttle lever position sensor  202  detects the position of the throttle lever  200  and the ECU  113  instructs the actuator  204  to adjust the position of the throttle valves  112 . 
     Once the throttle lever  200  passes the planing speed position, the lost motion device  264  no longer absorbs the motion of the throttle lever  200 . The throttle lever  200  now directly adjusts the position of the throttle valves  112 . Correspondingly, the ECU  113  instructs the actuator  204  to no longer control the position of the throttle valves  112 . 
     This arrangement has several advantages. For example, the control system can be configured such that to achieve planing speeds, the throttle lever  200  only has to be rotated a small distance. That is, the actuator  200  can be configured to open the throttle valves  112  to a planing speed position in response to a small movement of the throttle lever  200 . Because personal watercraft  20  are operated mostly in the planing mode, this arrangement is beneficial because it provides the throttle lever  200  with a larger useful range of motion. Accordingly, it is easier for the operator to keep the watercraft  20  in the planing state. 
     It should also be appreciated that the arrangement of FIG. 6 can also be reversed. That is, the control system can be configured such that the throttle lever  200  directly adjusts the throttle valves  112  until the watercraft  20  reaches a planing state. After a planing state is reached, the lost motion device  262  absorbs the motion of the throttle lever  200  and the throttle lever  200  no longer directly adjust the throttle valves  200 . Accordingly, during planing the throttle valves  112  are controlled by the ECU  113  and adjusted by the actuator  204 . This arrangement ensures that the throttle lever has a “light touch” during planing speeds. Accordingly, the operator&#39;s fingers do not tire during long trips. 
     With reference to FIGS. 7-8 another embodiment of a power output control is illustrated. This embodiment utilizes several components that generally correspond with other embodiments already described herein and as such, like reference numerals will be used to designate like components. 
     A power output control assembly  300  includes a throttle lever position sensor  202  in communication with the throttle lever  200  (FIG. 4) and a throttle valve actuator  204 . As discussed above, the throttle lever  200  is positioned on the handlebar assembly  44  near the right grip  198 . Of course, the throttle lever  200  can comprise other types of operators, such as, for example, but without limitation, a thumb trigger, a push button, a twist grip, a pedal or the like. The throttle operator  200  also can be located else where on the watercraft  20  and/or assume a variety of orientations on the watercraft in order to ease operations. In any of these positions and configurations, as noted above, the operator can use the throttle lever  200  as an input for a power output request. Thus, when an operator desires more power output from the engine  68 , the operator can squeeze the lever  200 , and thereby issue a signal to the power output control assembly  300  for causing the engine  68  to increase its power output. 
     The throttle lever  200  is in communication with the throttle lever position sensor  202  such as through a throttle cable  302 , or other suitable connection designed to transmit a force to the throttle lever position sensor  202 , discussed in greater detail below. 
     The power output control assembly  300  preferably is located within the cavity  52  of the hull  22 . As described in detail below, the throttle lever position sensor  202  detects the position of the throttle lever  200  and transmits a signal indicative thereof to the throttle valve actuator  204 . The throttle valve actuator  204  opens and closes the throttle valves  112  in response. Accordingly, the throttle lever  200  indirectly controls the position of the throttle valves  112 , and thereby, the power output from the engine  68 . 
     With continued reference to FIGS. 7-9, the throttle lever position sensor  202  includes an elongated lever  304  with a depending shaft  308  that is suitably journaled for rotation within a housing  306 . The housing  306  is substantially waterproof and preferably made of a polymeric or resin based material. A nut  310  is attached to a threaded portion  312  of the shaft  308  and prevents the lever  304  from being lifted out of the housing  306 . One or more seals  313  surround the shaft  308  and prevent water from entering the hole  315  formed in the upper surface  317  of the housing  306 . 
     The lever  304  has a through hole  307  (of FIG. 8) formed toward an end thereof and is configured to receive and secure an end of the throttle cable  302   a . In the illustrated embodiment, the throttle cable  302   a  extends through the hole  307  and has a barrel  309  attached thereto to inhibit the throttle cable  302   a  from withdrawing from the hole  307  in the lever  304 . The opposing end of the throttle cable  302   a  is connected to the throttle lever  200 , as is generally known in the art. Thus, movement of the throttle lever  200  toward a full throttle position will tension the throttle cable  302   a , which in turn, will displace the lever  304 . Thus, displacement of the throttle lever  200  is translated into displacement of the lever  304  of the throttle lever position sensor  202 . Of course, other suitable methods of connecting the throttle cable  302   a  to the lever  304  will be recognized. For example, a push rod could be substituted to transmit both push and pull forces, a pull—pull cable configuration could be used to force the lever  304  to rotate, or a torsion cable could transmit rotating forces. Additionally, the throttle cable  302   a  can be connected to the lever  304  through other suitable methods, such as tying, adhesives, or otherwise affixing it to the lever  304 . 
     An internal wall  314  divides the housing  306  into an upper chamber  316  and a lower chamber  318 , as viewed in FIG.  7 . However, it is to be noted that FIG. 7 is a partial top plan and sectional view of the assembly  300 . Thus, the upper chamber  316  is disposed on the starboard side of the assembly  316 , and the lower chamber  318  is disposed on the port side. These special relationships are also true for other components noted below referred to as “upper” and “lower” as well. Further, the illustrated orientation is merely one example of numerous other positions and orientations in which the assembly  300  can be placed. 
     Within the upper chamber  316  is a substantially watertight case  320  containing the throttle lever position sensor  202 . The lower chamber  318  houses the actuator  204 . 
     The case  320  is joined to the upper chamber, such as by a bolt  322  at a mating flange  324 . The case  320  further has a partition  326  running therethrough with a hole  328  formed therein configured to receive the lever shaft  308 . The partition  326  thus separates the case into an upper partition  327  and lower partition  329 . A torsional spring  220  is connected to the lever shaft  308 . The spring  220  biases the lever shaft  308  to a position corresponding with a throttle idle position, which is indicated by line I of FIG.  8 . The lower partition  329  houses the electronics of the throttle lever position sensor  202 . 
     In the illustrated arrangement, the components of the throttle lever position sensor  202  form a rheostat. A rheostat is a current-setting device in which one terminal is connected to a resistive element and the second terminal is connected to a movable contact to place a selective section of the restive element into the circuit. The current set by the rheostat comprises the signal indicating the position of the throttle lever  200 . It should be appreciated that other circuits could be used in the throttle lever position sensor  202 , such as, for example, a potentiometer. In such a system, the voltage set by the potentiometer would indicate the position of the throttle lever  200 . However, in the illustrated embodiment of the throttle lever position sensor  202 , a rheostat is preferred because it uses a small number of parts and is particularly suited for rugged use. 
     The throttle lever position sensor  204  comprises a movable contact  228  attached to an arm  230 . The arm  230  includes annular sleeve  231  that includes slots (not shown). The sleeve  231  fits over splines  332  formed on the lower end of the shaft  308 . A C-ring  330  secures the sleeve  231  at an axial position along the shaft  308 . Because the arm  230  and the shaft  308  are spline coupled together, the movable contact  228  rotates with the lever  304 , which rotates in response to rotation from the throttle lever  200 . 
     The moveable contact  228  is made of conductive material, such as, for example, copper. The moveable contact  228  includes a first contact point  234  and a second contact point  236 . The first contact point  234  contacts a resistive element  238 , which is attached to a lower surface  233  of the lower partition  329 . The resistive element  238  can be manufactured from any suitable material such as, for example, a carbon composition film, a metallic film, or a wire-wound resistor. As shown in FIG. 8, the resistive element  238  is arc-shaped. Accordingly, as the throttle lever  200  is rotated, the first contact point  234  remains in contact with the resistive element  238 . 
     The second contact point  236  of the moveable contact  228  contacts a stationary contact  240  that is mounted to a side wall  237  of the housing  306 . The side wall  237  and the stationary contact  240  are also arc-shaped such that as the throttle lever  200  rotates the arm  230 , the second contact  236  stays in contact with the stationary contact  240 . The stationary contact  240  is also made of a conductive material such, for example, copper. 
     A first electric wire  242  is connected to the resistive element  238 . Similarly, a second electric wire  244  is connected to the stationary contact  240 . Both wires  242 ,  244  are protected by a casing  243  and are routed through the watercraft  20  and connect to the ECU  113 . A closed circuit consisting of the ECU  113 , the first wire  242 , the resistive element  238 , the moveable contact  228 , the stationary contact  240 , and the second wire  244  is formed. The ECU  113  supplies a voltage to the circuit and detects a current through the closed circuit. 
     The current i in the circuit indicates the position of the throttle lever  200  as will be explained below. When the throttle lever  200  is in the idling position, a small portion of the resistive element  238  is placed into the circuit. Accordingly, the circuit has a relatively small total resistance R I . Consequently, for a given voltage, the current i I  flowing through the circuit will be relatively large according to the equation V=iR. According to the equation, for a given V, i is inversely proportional to R. 
     In comparison, when the throttle lever  200  is in the full-throttle position, a larger portion of the resistive element  238  is placed into the circuit. Accordingly, the total resistance R FT  of the circuit is greater than the total resistance R I  of the circuit in the idling position. Consequently, the current i FT  flowing through the circuit is smaller than the current i I  flowing through the circuit in the idling position. Thus, for a given voltage the current i indicates the position of the throttle lever  200  in accordance with the linear relationship between i and R. The ECU  113  senses the current and determines the position of the throttle lever. 
     A wire  254  connects the ECU  113  to the actuator  204  located in the lower chamber  318 . The lower chamber  318  is substantially watertight and is formed of sidewalls  342 , the partition  314 , and a lower wall  344 . Preferably, one of the walls has a hole  346  formed therethrough to allow the passage of the wire  254 . Preferably, a seal  348  surrounds the wire  254  and fills the hole  346  to maintain the water tightness of the lower chamber  318 . Additionally, another hole  350  is formed into a wall  344  of the lower chamber  318  to provide a passage for a portion  352  of the actuator  204 . In the illustrated embodiment, the actuator  204  comprises an electric motor  354 , such as a stepper motor or servo motor. A seal  356  preferably surrounds the protruding portion of the actuator  204 , which in the illustrated embodiment is a motor output shaft  352 . 
     With additional reference to FIG. 9, the actuator further includes a pulley  250 . Bowden-wire cables  252 , or other suitable cables, are coupled to the pulley  250  and the throttle valves  112  such that rotation of the pulley  250  causes the throttle valves  112  to open and close. The throttle valve actuator  204  opens and closes the throttle valves  112  in response to a signal generated by the ECU  113 . 
     When the throttle lever  200  is in the idling position, the current i in the circuit is relatively large as explained above. The ECU  113  senses the large current and sends a signal to the actuator  204  to adjust the throttle valves  112  to the idling position. As the throttle lever  200  is moved towards the full throttle position, the current i in the circuit decreases. In response, the ECU  113  sends a signal to the actuator  204  to open the throttle valves  112 . In this manner, the throttle lever  200  indirectly controls the position of the throttle valves  112 . Of course, it will be recognized that moving the throttle lever to the idle position could produce a small current, rather than a large current as described. 
     With reference to FIG. 10, an alternative arrangement of the throttle lever position sensor  202  is shown that is separate from the actuator  204 . In the illustrated embodiment, the throttle lever position sensor  202  comprises the basic configuration as other embodiment described herein. Namely, a housing  306  is formed to be substantially watertight and is formed of any suitable material. The housing includes an upper wall  317  and a lower wall  324  having a mounting flange configured to receive a bolt  322  and nut  323  to effect mounting. The housing  306  may be mounted in any suitable location, for example, below the control mast  44  against upper deck  24  within the engine compartment  60 . 
     A partition  326  is provided to separate the housing  306  into an upper partition  327  and a lower partition  329 . The interior components of the housing  306 , including the shaft  308 , torsion spring  220 , and electronic components are substantially the same as described above with reference to alternative embodiments. Thus, further description of the specific configuration of the components contained within the housing  306  is not believed to be necessary. It is sufficient to note that the illustrated configuration of the housing of FIG. 10 allows the throttle lever position sensor  202  to be mounted almost anywhere about the watercraft  10  because its construction and mounting are independent of the throttle lever  200  and the actuator  204 . This provides greater flexibility for placing the throttle lever position sensor  202  in advantageous locations, such as in locations that offer greater protection from jarring during watercraft operation, reduced exposure to water, or allow easy maintenance access. One such suitable location is generally below the control mast  32  and against the deck  360  (of FIG. 2) within the engine compartment  60 . 
     With reference to FIG. 11, a throttle lever  200  is mounted adjacent the grip  198  of the handlebar assembly. The throttle lever  200  is operatively coupled to the throttle lever position sensor  202  as described herein, which may be by a throttle cable  302 . The throttle lever position sensor  202  is configured to detect the position of the driver-controlled throttle lever  200  and send a corresponding signal to the ECU  113  via a conducting wire  362 . The ECU, in turn, is in communication with the actuator  204  via a conducting wire  364 . 
     As described herein, the actuator  204  is coupled to the throttle valves  112 , such as by a pulley and a pull—pull cable  252  type connection to transmit a rotational output of the actuator  204  to the throttle valves  112 . Thus, the throttle lever  200  indirectly determines the position of the throttle valves  114  through electronic signals generated and sent between the throttle lever position sensor  204 , the ECU  113 , and the actuator  204 , and a mechanical coupling between the actuator  204  and the throttle valves  113 . 
     The throttle valves  112  are coupled together for simultaneous rotational movement by a throttle valve shaft  366 . The throttle valves  112  are rotatable within the air intake system between substantially closed positions and fully open positions corresponding with idle and full throttle engine operating conditions, respectively. The engine  68  receives a volume of intake air that is regulated by the position of the throttle valves  112 . Where a fuel injection system (not shown) is used to form fuel charges, the amount of injected fuel is determined by a desired air/fuel mixture ratio and is injected into the air flow moving through the associated throttle bodies, or directly into the combustion chambers and thereby determines the ferocity of the combustion process, and hence, the engine speed. Thus, the throttle lever  200  indirectly controls the position of the throttle valves  112  and hence, the engine speed. 
     A throttle position sensor  368  is provided to detect the position of the throttle valves  112  and send a corresponding signal to the ECU  113 . As discussed above in relation to FIG. 10, the throttle lever position sensor  202  need not be mounted adjacent the actuator  204 , but can be mounted remotely. However, while the throttle lever position sensor  202  may be mounted anywhere about the watercraft, it is preferably mounted within the hull  22 , and even more preferably within the engine compartment  60 . 
     In the illustrated embodiment of FIG. 11, the actuator can be connected directly to the throttle shaft  366 . For example, the shaft  352  of the motor  354  can be directly keyed to the throttle valve shaft  366  so as to directly drive the throttle valve shaft  366 . As such, certain components, such as the additional pulleys and cables utilized in the embodiment of FIG. 9, can be eliminated, thereby reducing cost. Additionally, where the integrated assembly  300  is used, the entire assembly  300  can be mounted in the vicinity of an end of the throttle valve shaft  366 , so as to allow the actuator  204  can be keyed to the throttle valve shaft  366  as noted above. 
     With reference to FIG. 12, one embodiment of a watercraft advantageously locates the throttle lever position sensor  202  within the engine compartment  60  at a location forward of the engine  68  and beneath the control mast  32  against the inner wall of the upper deck  24 , designated generally by the reference numeral  360  (of FIG.  2 ). 
     With reference to FIG. 13, an alternative location of the actuator  204  is illustrated. The throttle valves  112  are each located within an intake passage  186  to control the flow of induction air therethrough. The throttle valves  112  are connected together by a throttle valve shaft  366  for concurrent rotational movement within their respective intake passages  186 . As described above, an actuator  204  receives a signal from the ECU  113 , such as an electric signal traveling through a wire  364 , and instructs the actuator  204  to rotate the throttle valves  113 . 
     In the illustrated embodiment, the actuator is an electric motor  354  having an output shaft  352 . A motor output gear  370 , or motor gear, is attached to the output shaft  354  and configured to rotate therewith. A throttle valve gear  372  is mounted on one end of the throttle valve shaft  366  and is configured for concurrent rotation therewith. The throttle valve gear  372  is disposed in meshing engagement with the motor gear  370 . Thus, as the motor  354  turns the motor gear  370 , a rotational force is imparted to the throttle valve gear  372 , which turns the throttle shaft  366  and the attached throttle valves  112 . 
     The meshing gears  370 ,  372  can be of any common diametral pitch, so as to maintain their meshing engagement. Additionally, in one embodiment, it is preferred that the motor output shaft  352  is substantially parallel with the throttle valve shaft  366  to enable a simple gear mesh between the gears  370 ,  372 . To further enhance the simplicity of maintaining an effective meshing of the gears  370 ,  372 , one embodiment utilizes gears having an involute profile, which is relatively easy to manufacture, and does not require strict tolerances between the respective gear shafts. Of course, other gear types could be used, such as, for example, helical gears, bevel gears, or any such suitable configuration could be used with parallel or nonparallel gear shafts. 
     In one embodiment, the gear ratio is 1:1 so that an angular displacement a of the motor gear  370  results in a rotation of the throttle valve gear  372  the same angle a. In other embodiments, step down gearing is used to reduce the relative angular velocity of the throttle valve shaft  366  in comparison with the motor output shaft  352 . In this case, the motor gear  370  would be smaller than the throttle valve gear  372 . In other embodiments, step up gears are used in which the motor gear  370  is larger than the throttle valve gear  372 . This particular configuration provides very fast response of the throttle valves  112  because the throttle valve gear  372  is configured to turn faster than the motor gear  370 . However, while it results in a fast response time from the throttle valves  112 , the precision of the throttle valve position is reduced. 
     For example, assuming the motor  354  is accurate and steppable through one degree increments, the throttle valve gear  372  would be steppable through increments corresponding with the gear ratio. For instance, if the gear ratio were 1:2, a one degree rotation of the motor gear  370  would result in a two degree rotation of the throttle valve gear  372 . Thus, the throttle valve gear  372  would only be steppable through 2 degree increments in this configuration. However, any suitable and desired gear ratio can be selected based upon the combination of the desired speed and accuracy of the throttle valve position and upon the characteristics of the actuator  354 . 
     With reference to FIG. 14, another embodiment illustrates an arrangement of an engine and an associated power output control. As illustrated, a single throttle valve  112  is mounted in an induction system of the engine  68 . A throttle lever position sensor  202  is mounted remotely from the throttle lever  200  and grip  198 . The throttle lever position sensor  202  is in communication with the ECU  113  through a wire  362 . 
     As described above, the throttle lever position sensor  202  detects the position of the throttle lever  200  and sends a corresponding signal to the ECU  113 , which then sends a control signal to the actuator  204  through a wire  364 . The actuator  204  then controls the throttle valve  112  and adjust its opening degree in response to the signal sent by the ECU  113 . 
     The illustrated embodiment shows a single throttle valve  112  rotatably mounted on a throttle valve shaft  366 . The actuator  204  can be coupled to the throttle valve shaft  366  in any suitable manner. For example, the actuator  204  can be directly connected to the throttle valve shaft  366 , or can have an interposed coupling, such as meshing gears, or a cable system as already described. Of course, other suitable methods of transmitting the output of the actuator  204  to the throttle valve  112  are possible and will become readily apparent to one of ordinary skill in the art in light of the disclosure herein. 
     The throttle lever position sensor  202  can be suitably mounted anywhere on or within the watercraft. It is preferable that the throttle lever position sensor  202  is encased in a substantially watertight housing or case. Therefore, many preferred embodiments disclosed herein describe a waterproof case configured to house the components that make up the throttle lever position sensor  202 . Additionally, because in many embodiments the throttle lever position sensor  202  is connected to the throttle lever  200  by a single cable or wire, there are relatively few constraints on the required positioning of the throttle lever position sensor  202 . 
     Likewise, there are relatively few constraints on the required positioning of the actuator. However, it is desirable to provide a substantially watertight case to house the actuator  204 . Therefore, many embodiments disclosed herein describe a substantially watertight or waterproof case designed to house the components of the actuator  204 . Many embodiments also describe that it is preferable that the actuator  204  is located within close proximity to the throttle valves  112  because there is usually a mechanical coupling between the two. The mechanical coupling can be of any suitable type configured to translate the output of the actuator  204  into adjustment of the throttle valve  112  position. In some embodiments, this mechanical coupling is in the form of a gear pair. Other embodiments utilize a direct connection of the actuator  204  output, such as a motor output shaft, to the throttle valve shaft  366 . Still, other embodiments describe the use of Bowden-wire type cable connections to transmit a rotational force from the actuator  204  to the throttle valves  112 . 
     According to the embodiment of FIG. 15, throttle valves  112  are connected to a common rotatable throttle valve shaft  366 . The throttle valves  112  are positioned within air intake passages  186  and configured to vary their opening degree to regulate the flow of intake air through the intake passages  186 . One end of the throttle valve shaft  366  carries a throttle pulley  374  that is constrained to rotate with the throttle valve shaft  366  and accompanying throttle valves  112 . An actuator, such as a motor  354 , is mounted adjacent the throttle valves  112  and is operatively coupled to the throttle valve shaft  366 . 
     In the illustrated embodiment, the motor  354  has an output shaft  352  that is configured for rotation with the motor  354 . The output shaft  352  further carries a motor pulley  250  that is likewise rotatable by the motor  354 . The motor pulley is coupled to the throttle pulley  374  by any suitable connection  376 . As described above, alternative embodiments use various methods of effecting the operative coupling between the motor pulley  250  and throttle valve shaft  366 . For example, the connection  376  is in the form of a push-pull cable, a Bowden-wire type cables, other types of pull—pull cable arrangements, a belt-drive system utilizing any suitable belt configuration and cross section, or other suitable connection methods which will allow the output of the motor  354  to be transferred into throttle valve  112  adjustment. 
     From the foregoing description, it is readily apparent that the illustrated throttle control system embodiments have several advantages over prior art control systems. For example, prior art throttle valves are normally biased to an idling position by return springs. These return springs are generally relatively stiff in order to overcome the force of air flow across the throttle valve. The prior art throttle levers are typically directly coupled to the throttle valve. Accordingly, the operator must hold the throttle lever against the force of the return springs in order to maintain a desired speed. In comparison, the throttle lever  200  in the illustrated embodiments of the throttle control system indirectly controls the throttle valves  112 . That is, the actuator  204  opens and closes the throttle valves in response to the detected position of the throttle lever  200 . The return spring  220  returns the throttle lever  200  to the idling position. The return spring is not balanced against the closing force on the throttle valves  112  due to airflow. Accordingly, the return spring  220  can be designed to be significantly weaker than the throttle valve return springs of the prior art. Accordingly, the throttle lever  200  has a “light touch” and the operator&#39;s fingers becomes less tired after holding the throttle lever  200  for a long period of time. 
     Of course, the foregoing description is that of certain features, aspects and advantages of the present invention to which various changes and modifications may be made without departing from the spirit and scope of the present invention. Moreover, a watercraft need not feature all objects of the present invention to use certain features, aspects and advantages of the present invention. The present invention, therefore, should only be defined by the appended claims.