Abstract:
A throttle linkage for use with an internal combustion engine is disclosed which connects a throttle actuator to a throttle assembly. The throttle linkage is nonadjustable and interacts with a plurality of throttle stops integrally formed with an engine block. Such an arrangement prevents tampering in advanced two-stroke engines and ensures emission output at a level well below that allowed.

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to engine throttle controls, and more particularly, to a nonadjustable throttle linkage connecting a throttle assembly to a throttle input. 
     During operation of most internal combustion engines, an operator increases the operating speed of the engine by increasing a throttle actuator. In highway vehicles, the throttle actuator is commonly referred to as a gas pedal or, in motorcycle-type devices, a twist hand grip accelerator. In non-highway use engine equipped devices, the accelerator is often generically referred to as the throttle or a throttle actuator. In watercraft, the throttle actuator is often located near a control station, or bridge, and is often a hand lever having linear motion that an operator adjusts in order to manipulate the operating speed of an engine in communication therewith. 
     The throttle actuator is often connected to a throttle linkage assembly that is connected to a throttle assembly mounted directly about an engine. The throttle assembly generally includes a throttle body having an opening therethrough, a throttle plate positioned in the opening of the throttle body, and an actuator connected to the throttle plate. Commonly, the throttle linkage connects the throttle assembly to the operator controlled throttle actuator such that movement of the throttle actuator results in a change of position of the throttle plate of the throttle assembly. As an operator desires to increase the operating speed of the engine, and the engine demands more combustion gas in response to the desired increase in engine speed, the operator advances the throttle actuator which in turn rotates the throttle plate relative to the throttle body opening. 
     Generally, as an engine is accelerated, the combustion process requires more fuel and more combustion air. As an operator advances the throttle actuator, the throttle plate opens, thereby allowing more combustion air to pass to the combustion chambers of the engine. The movement of the throttle plate relative to the movement of the throttle actuator is partly dependent on the throttle linkage disposed therebetween. In an effort to better control the responsiveness of the engine and allowance for tolerance, the throttle linkage disposed between the throttle assembly and the throttle actuator often includes some form of adjustment, such as independently adjustable links. In older engines, the adjustability of the links was also used to set idle speed. 
     The throttle linkage assembly can also be adjustable relative to a plurality of throttle stops. Such adjustment means often includes a plurality of screws that restricts the movement of individual links. Movement of the throttle links is often minimally fixed between fixed throttle stops. The throttle linkage is often adjusted relative to a first throttle stop to set an idle throttle linkage position that corresponds to an idle engine speed. Adjusting the throttle linkage relative to the first throttle stop often determines the relation of the throttle linkage to the throttle plate to ensure smooth and repeatable idle engine operation. As these older engines are operated, an operator could acoustically determine when the preferred idle orientation occurs. In much the same way, a second throttle stop is often implemented to set a wide open throttle position. Improper adjustment of the throttle linkage from the first or second throttle stops results in rough running engine idle speed, engine stall, or a fast running idle engine speed. Additionally, operating an engine at any of these conditions for extended periods of time results in inefficient use of engine fuel and detrimentally affects engine emissions. 
     Drawbacks to the adjustability of the throttle linkage assembly includes the adjustment means inadvertently coming loose and operator tampering. If the throttle linkage adjustment inadvertently comes loose, the engine may be operated outside a preferred range without operator knowledge. While any change in the operation of the engine with the adjusted linkage orientation may be imperceptible to the operator, fuel efficiency and engine emissions are affected. Similarly, an operator may adjust the throttle linkage outside of it&#39;s preferred operating range in a effort to improve the perceived operation of the engine. Such manipulation can result in damage to engine components not limited to the throttle assembly. Particularly in two-cycle engines where the fuel and air supplied to the engine perform cooling functions during operation, manipulation of the throttle assembly resulting in changes to the flow of combustion fluids through the engine can lead to overheating of engine components. 
     While many believe that two-stroke engines are generally not environmentally friendly engines, such preconceptions are misguided in light of contemporary two-stroke engines. Modern direct injected two-stroke engines and, in particular, Evinrude® outboard motors, are compliant with, not only today&#39;s emission standards, but emission standards well into the future. However, since these engines are so advanced, they require trained technicians perform certain repairs and adjustments. As such, a significant portion of the ability to adjust these motors has been eliminated or restricted to qualified personnel in an effort to ensure the future emission efficiency of the en- gines. 
     It would therefore be desirable to have a throttle linkage and method of manufacturing an engine with a throttle linkage where the throttle linkage has no means of adjustment. 
     BRIEF DESCRIPTION OF INVENTION 
     The present invention provides a throttle linkage and method of manufacturing an engine that solves the aforementioned problems. The present invention provides a throttle linkage having a plurality of throttle links. The throttle linkage is connectable between a throttle actuator and a throttle assembly and has a permanently set range of operation. Such a throttle linkage is permanently calibrated and tamper resistant. 
     In accordance with one aspect of the present invention, a throttle linkage for an outboard motor is disclosed which includes an input end and an output end. The input end of the throttle linkage is constructed to receive an operator throttle command initiated in a watercraft and the output end is constructed to be directly connected to a throttle assembly of an engine disposed in an outboard motor. A lever assembly having a plurality of lever arms is disposed between the input end and the output end wherein each lever arm and the lever assembly have no means for adjusting the lever assembly. Such a construction forms a throttle linkage that is nonadjustable. 
     According to another aspect of the present invention, a throttle linkage for an engine is disclosed that includes a first link, a second link, and a third link. The first link is rotatably attached to an engine and has a permanently fixed range of rotation. An input arm is integrally formed with the first link and connectable to a throttle cable. The second link also has a permanently fixed range of rotation and is engagable by an output arm of the first link. The third link is connected to an output arm of the second link and connected to a throttle assembly. Such a construction forms a throttle linkage without a variable, or adjustable, range of rotation. 
     In accordance with yet another aspect of the present invention, an internal combustion engine is disclosed which includes an engine block having at least one cylinder formed therein. A throttle assembly having an opening therethrough is in fluid communication with the at least one cylinder. A throttle linkage free of any form of adjustment is connected to the throttle assembly and is constructed to receive a throttle command. The throttle linkage has at least one link having an index integrally formed therewith. The index of the at least one link is constructed to directly engage an at least one throttle stop extending from the engine block. Such a construction forms a throttle linkage without an adjustment means disposed between the throttle link and the throttle stop. 
     According to a further aspect of the present invention, a method of manufacturing an engine is disclosed which includes the steps of: forming a throttle link having a tab; forming an engine block with at least one throttle boss; and attaching the throttle link to the engine with a permanently fixed range of movement and with the tab rotatably related permanently to the throttle boss. 
     Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention. 
       In the drawings: 
         FIG. 1  is a perspective view of an exemplary outboard motor incorporating the present invention. 
         FIG. 2  is an elevational view of a portion of the outboard motor of  FIG. 1  showing the throttle linkage and throttle assembly of the present invention. 
         FIG. 3  is an exploded view of the throttle body and throttle assembly of  FIG. 2 . 
         FIG. 4  is a cross-sectional view of a portion of the throttle assembly of  FIG. 3  taken along line  4 — 4  and shows a throttle assembly idle position. 
         FIG. 5  is a cross-sectional view of a portion of the throttle assembly of  FIG. 3  taken along line  5 — 5  and shows a closed throttle plate position. 
         FIG. 6  is a view similar to  FIG. 4  and shows the throttle assembly in a throttle assembly transition position. 
         FIG. 7  is a view similar to  FIGS. 4 and 5  and shows the throttle assembly rotated past the throttle assembly transition position. 
         FIG. 8  is a view similar to  FIG. 5  and shows the throttle assembly with the throttle plate rotated beyond the closed throttle plate position. 
         FIG. 9  is a detail view of the throttle assembly of  FIG. 2  with the throttle actuator, throttle linkage assembly, and throttle assembly in an idle throttle position. 
         FIG. 10  is a detail view of the throttle linkage assembly in the idle throttle position as shown in  FIG. 9 . 
         FIG. 11  is a detail view showing the throttle actuator, throttle linkage assembly, and throttle assembly of  FIG. 9  advanced to an engine transition position. 
         FIG. 12  is a detail view showing the throttle actuator, throttle linkage assembly, and throttle assembly of  FIG. 9  advanced to a wide open throttle position. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates generally to internal combustion engines. In the present embodiment, the engine is a direct fuel injected, spark-ignited two-cycle gasoline-type engine.  FIG. 1  shows an outboard motor  10  having one such engine  12  controlled by an electronic control unit (ECU)  14  under engine cover  16 . Engine  12  is housed generally in a powerhead  18  and is supported on a mid-section  20  configured for mounting on a transom  22  of a boat  24  in a known conventional manner. Engine  12  is coupled to transmit power to a propeller  26  to develop thrust and propel boat  24  in a desired direction. A lower unit  30  includes a gear case  32  having a bullet or torpedo section  34  formed therein and housing a propeller shaft  36  that extends rearwardly therefrom. Propeller  26  is driven by propeller shaft  36  and includes a number of fins  38  extending outwardly from a central hub  40  through which exhaust gas from engine  12  is discharged via mid-section  20 . A skeg  42  depends vertically downwardly from torpedo section  34  to protect propeller fins  38  and encourage the efficient flow of outboard motor  10  through water. 
     A throttle body  50  (shown in phantom), is connected to engine  12  and has at least one opening  52  passing therethrough. The number of openings generally corresponds to a number of cylinders in engine  12 . Only one is shown for a two-cylinder engine for exemplary reasons. Opening  52  is often referred to as an air intake opening and allows combustion gas, generally air, to pass through throttle body  50  and into engine  12 . Another opening  53 , an idle air bypass, passes through throttle body  50  and provides an alternate path for combustion gas into and through throttle body  50 . As will be described further below, opening  53  is constructed to provide combustion gas to engine  12  during idle and low speed operations. 
       FIG. 2  shows outboard motor  10  with a portion of engine cover  16  cut away. A throttle cable  54  connects a throttle actuator  55  to a throttle linkage assembly  56  so that throttle linkage assembly  56  is movable in response to operator manipulation of throttle actuator  55 . Throttle cable  54  passes through an opening  58  formed in engine cover  16 . A mounting bracket  60  secures throttle cable  54  to throttle body  50  and prevents movement therebetween. Throttle cable  54  has a cable  62  which extends from an end  63  thereof. Cable  62  extends and retracts from throttle cable  54  relative to mounting bracket  60  in response to operator manipulation of throttle actuator  55 . An end  64  of cable  62  engages a first throttle link  66  of throttle linkage assembly  56 . Cable end  64  is attached to a first arm  68  of first throttle link  66  so that movement of cable  62  results in rotation of first throttle link  66  about a pin or mounting bolt  70 . 
     A second arm  72  of first throttle link  66  engages a pin  74  extending from a second throttle link  76  of throttle linkage assembly  56 . Second throttle link  76  rotates about a pin  78  and has a third throttle link  80  attached thereto. A first end  82  of third throttle link  80  is connected to an end  84  of second throttle link  76 . A second end  86  of third throttle link  80  is attached to an actuator  88  of a throttle assembly  92 . During operation, as an operator advances throttle actuator  55 , throttle cable  62  moves and rotates first throttle link  66  of throttle link assembly  56  about pin  70 . Rotation of first throttle link  66  causes second arm  72  to engage pin  74  and thereby rotate second throttle link  76 . Displacement of second throttle link  76  is translated to throttle assembly  92  via third throttle link  80  so that actuator  88  is coupled to throttle actuator  55 . Such a linkage forms a throttle assembly that is highly responsive and sensitive to operator manipulation of a throttle actuator. 
     Referring to throttle assembly  92 , a mount  89 , preferably having a throttle position sensor (TPS)  90  inside, is connected proximate a first end  91  of actuator  88 . The TPS  90  communicates the position of actuator  88  to the ECU of engine  12 . In addition to the responsiveness of the throttle assembly, mounting TPS  90  about the actuator of the throttle assembly ensures that an ECU attached thereto is nearly instantaneously aware of operator manipulation of throttle actuator  55 . Such a construction connects a throttle linkage assembly and throttle assembly with reduced play therebetween and allows an engine  12  so equipped to be highly responsive to actual throttle position. 
       FIG. 3  shows an exploded view of throttle assembly  92 . Throttle body  50  is mounted to engine  12  with opening  52  in fluid communication with the combustion chambers of engine  12  and in general alignment with a front  51  of engine  12 , as best viewed in  FIG. 1 . The front  55  of engine  12  is in linear alignment with an operator and passengers of watercraft  24 . Referring back to  FIG. 3 , throttle plate  94  is rotatably positioned within opening  52  to regulate air flow through throttle body  50 . During idle operation of engine  12 , throttle plate  94  remains closed, as shown in  FIGS. 3 and 5 , and combustion gas is provided to engine  12  via an opening or idle air bypass  53 . Opening  53  provides a path for combustion gas into engine  12  when throttle plate  94  prevents the passage of combustion gas through opening  52 . Opening  53  is formed in throttle body  50  generally opposite air intake opening  52  and faces generally towards engine  12  and away from the operator and passengers of the watercraft or other recreational product. 
     Throttle plate  94  is secured to a throttle shaft  96  by a plurality of fasters  98  such that rotation of throttle shaft  96  results in rotation of throttle plate  94 . A spring  100  is positioned about a first end  102  of throttle shaft  96  and biases throttle plate  94  to a closed position in opening  52 , as shown in  FIG. 3 . A second end  104  of throttle shaft  96  extends through a mount structure  106  of throttle body  50 . A pin  108 , preferably a roll pin, extends through throttle shaft  96  and engages a second end  110  of actuator  88 . A bushing  112  is constructed to fit about mount  106  and facilitates rotation of actuator  88  relative thereto. 
     Third throttle link  80  engages an arm  114  of actuator  88 . Arm  114  is integrally formed with actuator  88  and extends from a body  115  thereof. By extending from body  115  of actuator  88 , arm  114  allows for a generally linear translation of third throttle link  80  to rotate actuator  88 . Body  115  has a generally cylindrical shape and extends from first end  91  of actuator  88  to second end  110 . First end  91  of actuator  88  has a bearing surface  118  thereabout and an extension, or tab  120 , extending therefrom. Tab  120  is constructed to engage throttle position sensor  90  located within mount  89  such that movement of actuator  88  results in a change of signal from throttle position sensor  90 . Throttle position sensor  90  is within a mount  89  positioned about first end  91  of actuator  88 . It is understood that in those applications where a throttle position sensor is mounted remotely relative to a throttle shaft that throttle position sensor  90  can be merely a molded mount attachable to the throttle body and constructed to support an end of the actuator therebetween. 
     A flange  122  of TPS mount  89  engages bearing surface  118  of actuator  88  and maximizes a frictionless rotational engagement therebetween. A plurality of fasteners  124  and corresponding washers  126  secure TPS mount  89  to throttle body  50  at a boss, or mounting flange  128 , extending from throttle body  50 . Mounting flange  128  includes a pair of holes  130  constructed to receive fasteners  124  therein to secure TPS mount  89  to throttle body  50  with actuator  88  disposed therebetween. Actuator  88  is free to rotate relative to throttle body  50  and TPS mount  89 . As such, operator manipulation of throttle actuator  55 , show in  FIG. 2 , moves third throttle link  80  which in turn rotates actuator  88  relative to throttle body  50  and TPS mount  89 . 
     A temperature probe  132  extends through throttle body  50  into air intake opening  52  on an engine side  133  of throttle plate  94  and is in electrical communication with ECU  14  shown in  FIG. 2 . Referring back to  FIG. 3 , temperature probe  132  is positioned in air intake opening  52  such that it does not interfere with rotation of throttle plate  94 . Temperature probe  132  communicates to the ECU a temperature of combustion air provided to the engine to allow the ECU to more effectively control overall engine efficiency and, particularly, fuel combustion efficiency. 
     Actuator  88 , TPS mount  89 , bushing  112 , and throttle shaft  96  all share a common axis  134 . Common axis  134  is the axis of rotation of throttle shaft  96  to which throttle plate  94  is mounted. Although mounted about throttle shaft  96  and directly responsive to operator movement of throttle actuator  55 , actuator  88  is partially rotatable about common axis  134  without affecting the position of throttle plate  94 . That is, throttle plate  94  remains closed, as shown in  FIG. 3 , through a predetermined range of operator movement of throttle actuator  55 , yet the RPM of the engine increases, as will be described in further detail below with respect to  FIGS. 4–9 . 
     As shown in  FIG. 4 , when assembled, throttle shaft  96  and pin  108  of throttle assembly  92  are positioned in a recess  136  of actuator  88 . Recess  136  has a bowtie shaped cross-section  137  that allows partial rotation of pin  108  and shaft  96  relative thereto. Although shown having a bowtie shaped cross-section it is understood that such a cross-section is merely by way of example and that other arrangements could be used to achieve the result of allowing actuator  88  to determinably engage and disengage from a driving relationship with throttle shaft  96 , thereby providing a “deadband” in the throttle linkage. An example of such an arrangement would be a portion of the recess constructed to receive the throttle shaft and another portion of the recess constructed to receive a keying element such as one end of a pin extending from the shaft. 
     The relation of actuator  88  to pin  108 , as shown in  FIG. 4 , indicates an idle throttle position. Comparing  FIG. 4  to  FIG. 6 , as an operator advances throttle actuator  55 , third throttle link  80  is advanced a distance of X′, as shown in  FIG. 6 . The relation of actuator  88  to pin  108 , as shown in  FIG. 6  indicates a transition throttle position. The transition throttle position is generally defined as the point during engine operation where the combustion process preferably transitions from a stratified combustion operation to a homogeneous combustion operation wherein stratified and homogenous define the type of combustion charge supplied to the engine, as is known in the art. 
     The displacement of third throttle link  80  distance X′ results in rotation of actuator  88  but does not move pin  108  or throttle shaft  96 . When third throttle link  80  is displaced distance X′, actuator  88  rotates a distance Y′. In one embodiment, distance Y′ is not more than 35 degrees and is preferably approximately 19 degrees. During operation, although an operator has advanced throttle actuator  55  and displaced third throttle link  80  a distance of X′, as shown in comparing  FIGS. 4 and 6 , recess  136  prevents actuator  88  from displacing throttle shaft  98 . As such, throttle plate  94  remains closed, as shown in  FIG. 5 , as actuator  88  is rotated relative thereto. Such a construction forms the deadband in the throttle assembly. One exemplary explanation of the deadband is where the throttle assembly receives an input command having a value of X′ and throttle plate  94  does not experience a corresponding output. Such a construction allows throttle plate  94  to remain closed for a predetermined range of engine operation, not merely an engine idle condition. 
     Throttle plate  94  remains closed, as shown in  FIG. 5 , up to the transition of throttle position shown in  FIG. 6 . By maintaining throttle plate  94  closed until approximately the point the engine requires a homogenous combustion charge, a minimum amount of engine noise is allowed to exit the engine through air intake opening  52 , while air bypass  53  is sized large enough to provide an adequate charge. By the time that the engine requires a generally homogenous combustion charge, and the throttle plate begins to open with further advancement of the throttle actuator, the overall operating noise of the engine reaches a level that overcomes any noise that may exit the engine through the air intake opening  50 . Maintaining throttle plate  94  closed beyond engine idle speed reduces the overall amount of engine noise allowed to exit the engine through air intake opening  52 . 
     Comparing  FIGS. 6 and 7 , as an operator advances the throttle actuator beyond a distance X′, shown in  FIG. 6 , any further increase in the position of the throttle actuator provides a corresponding rotation of throttle shaft  96  and opens throttle plate  94 . As shown in  FIG. 7 , as third throttle link  80  is advanced a distance X″, actuator  88  is rotated an angle of Y″ while throttle shaft  96  rotates an angle of Z″. The difference between Y″ and Z″ is equal to the amount of deadband engagement—distance Y′, as shown in  FIG. 6 , between actuator  88  and throttle plate  94 . Once third throttle link  80  is displaced a distance greater than X′, as shown in  FIG. 6 , any further displacement of third throttle link  80  results in rotation of throttle shaft  96 , as shown in  FIG. 7 . A leading edge  138  of recess  136  engages pin  108  and rotates throttle shaft  96 . As leading edge  138  comes into contact with pin  108 , as shown in  FIGS. 7 and 8 , throttle plate  94  rotates relative to opening  52  of throttle body  50 . As shown in  FIG. 8 , when the throttle actuator is advanced beyond the transition throttle position, throttle plate  94  rotates to an open position, indicated by a gap  140  formed between throttle plate  94  and throttle body  50 , allowing combustion gas to pass through opening  52 . 
     During idle operation of outboard motor  10 , as shown in  FIG. 9 , when throttle actuator  55  is in an idle throttle position  142 , throttle plate  94  is disposed generally across opening  52  thereby preventing the passage of combustion gas therethrough. Opening  53  provides combustion gas to pass through throttle body  50  thereby providing idle operation combustion gas to engine  12 . Second arm  72  of first throttle link  66  includes a cam, or cam face  144  constructed to engage pin  74  of second throttle link  76 . 
     As shown in  FIG. 10 , at idle operation of engine  12 , a small gap  146  is formed between cam face  144  of first throttle link  66  and pin  78  of second throttle link  76 . First throttle link  66  includes a tab, or third arm  148  integrally formed therewith. Third arm  148  is constructed to engage a first throttle stop  150  and a second throttle stop  152 . Throttle stops  150 ,  152  are integrally formed with engine  12  and restrict the movement of throttle linkage  56  and define an idle throttle linkage position, as shown in  FIGS. 9 and 10 , and a wide open throttle linkage position, as shown in  FIG. 12 . Such a construction forms a throttle linkage assembly having no means of adjustment and wherein the range of rotation of each of the links of the throttle linkage assembly is permanently fixed. 
     Referring back to  FIG. 9 , with throttle actuator  55  in idle throttle position  142 , third arm  148  of first throttle link  66  abuts first throttle stop  150  thereby permanently fixing the engine idle throttle linkage positions. Cam face  144  of second arm  72  of first throttle link  66  disengages from pin  74  with gap  146  therebetween. During idle throttle position  142 , second throttle link  76 , third throttle link  80 , and actuator  88  are maintained in an idle position and mechanically separated from throttle actuator  55  by gap  146  between first and second throttle links  66 ,  76 . 
     As shown in  FIG. 11 , throttle actuator  55 , throttle linkage assembly  56 , throttle assembly  92  have been advanced to their respective engine transition positions  154 . Throttle actuator  55  is shown advanced to a transition displacement, indicated by arrow  156 , of throttle cable  62 . Displacement  156  rotates first throttle link  66  such that third arm  148  disengages from first throttle stop  150  and rotates toward second throttle stop  152 . Cam face  144  engages pin  74  of second throttle link  76  and slides there along rotating second throttle link about pin  78 . Second throttle link  76  rotates in the direction of arrow  158  and displaces third throttle link  80  in the direction of arrow  160 . Displacement  160  of third throttle link  80  rotates actuator  88  indicated generally by arrow  162 . 
     Throttle position sensor  90  signals to the ECU the movement  162  of actuator  88 . The ECU, in response to the signal from throttle position sensor  90 , adjusts predetermined engine operating parameters. One of the engine parameters that is adjusted is the amount of fuel provided to the engine. The amount of fuel provided to the engine is increased in response to the throttle actuator adjustment. By adjust the amount of fuel provided to the engine at transition throttle position  154 , the operating speed of the engine is increased. Even though the operating speed and the amount of fuel provided to the engine is increased, from idle throttle position  142 , shown in  FIG. 9 , to transition throttle position  154  shown in  FIG. 11 , throttle plate  94  remains closed. This is accomplished because the air bypass  53  allows sufficient air induction into the engine via a second opening. 
       FIG. 12  shows a wide open throttle position  164 . Throttle actuator  55  is fully advanced. Third arm  148  of first throttle link  66  is rotated into contact with second throttle stop  152 . Second throttle stop  152  permanently fixes the position of throttle linkage assembly  56  and throttle assembly  92  during wide open throttle operation. Third throttle link  80  rotates actuator  88  beyond transition throttle position  154 , as shown in  FIG. 11 , so that actuator  88  engages throttle plate  94 . As shown in  FIGS. 11 and 12 , when the throttle actuator is advanced beyond transition throttle position  154  to wide open throttle position  164 , throttle plate  94  rotates approximately 90 degrees relative to opening  52  thereby allowing combustion gas to pass therethrough. As engine  12  needs more combustion gas to mix with the fuel in order to transition from the stratified combustion stage to a homogeneous combustion stage, throttle plate  94  rotates in opening  52  to allow more combustion gas to pass therethrough. By maintaining the throttle plate closed across opening  52  during relatively low speed operation of engine  12 , throttle assembly  92  reduces the amount of engine noise emitted toward an operator. 
     Therefore, in accordance with one embodiment of the present invention, a throttle linkage for an outboard motor includes an input end and an output end. The input end of the throttle linkage is constructed to receive an operator throttle command initiated in a watercraft and the output end is constructed to be directly connected to a throttle assembly of an engine disposed in an outboard motor. A lever assembly having a plurality of lever arms is disposed between the input end and the output end wherein each lever arm and the lever assembly have no means for adjusting the lever assembly. 
     According to another embodiment of the present invention, a throttle linkage for an engine includes a first link, a second link, and a third link. The first link is rotatably attached to an engine and has a permanently fixed range of rotation. An input arm is integrally formed with the first link and connectable to a throttle cable. The second link also has a permanently fixed range of rotation and is engagable by an output arm of the first link. The third link is connected to an output arm of the second link and connected to a throttle assembly. 
     In accordance with yet another embodiment of the present invention, an internal combustion engine includes an engine block having at least one cylinder formed therein. A throttle assembly having an opening therethrough is in fluid communication with the at least one cylinder. A throttle linkage free of any form of adjustment is connected to the throttle assembly and is constructed to receive a throttle command. The throttle linkage has at least one link having an index integrally formed therewith. The index of the at least one link is constructed to directly engage an at least one throttle stop extending from the engine block. 
     According to a further embodiment of the present invention, a method of manufacturing an engine includes the steps of: forming a throttle link having a tab; forming an engine block with at least one throttle boss; and attaching the throttle link to the engine with a permanently fixed range of movement and with the tab rotatably related permanently to the throttle boss. 
     While the present invention is shown as being incorporated into an outboard motor, the present invention is equally applicable with many other applications and recreational products, some of which include inboard motors, snowmobiles, personal watercrafts, all-terrain vehicles (ATVs), motorcycles, mopeds, lawn and garden equipment, generators, etc. 
     The present invention has been described in terms of the preferred embodiment, and it is recognized that equivalents, alternatives, and modifications, aside from those expressly stated, are possible and within the scope of the appending claims. While the present invention is shown as being incorporated into an outboard motor, the present invention is equally applicable with other recreational products, some of which include inboard motors, snowmobiles, personal watercrafts, all-terrain vehicles (ATVs), motorcycles, mopeds, power scooters, and the like. Therefore, it is understood that within the context of this application, the term “recreational product” is intended to define products incorporating an internal combustion engine that are not considered a part of the automotive industry. Within the context of this invention, the automotive industry is not believed to be particularly relevant in that the needs and wants of the consumer are radically different between the recreational products industry and the automotive industry. As is readily apparent, the recreational products industry is one in which size, packaging, and weight are all at the forefront of the design process, and while these factors may be somewhat important in the automotive industry, it is quite clear that these criteria take a back seat to many other factors, as evidenced by the proliferation of larger vehicles such as sports utility vehicles (SUV).