Patent Publication Number: US-9403586-B2

Title: Jet propelled watercraft

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a jet propelled watercraft. 
     2. Description of the Related Art 
     United States Patent Application Publication No. 2013/0344754 discloses a jet propelled watercraft that includes a first accelerator operator (accelerator operator) provided in a right grip of a handle and a second accelerator operator (reverse gate operator) provided in a left grip of the handle. The jet propelled watercraft further includes an engine, a jet pump driven by the engine, a reverse gate, a shift actuator, and an ECU. The shift actuator moves the reverse gate to a forward drive position, a neutral position, and a reverse drive position. The ECU controls the engine and the shift actuator. 
     The first accelerator operator is mainly operated to drive the jet propelled watercraft forward. The second accelerator operator is mainly operated to drive the jet propelled watercraft in reverse or to reduce a forward speed of the jet propelled watercraft. The reverse gate can be disposed at the reverse drive position by operating the second accelerator operator. An operation amount of the first accelerator operator is detected by a first accelerator position sensor and an operation amount of the second accelerator operator is detected by a second accelerator position sensor. Based on the operation amounts of the first and second accelerator operators detected by the first and second accelerator position sensors, the ECU controls an engine speed (throttle opening degree) and a shift position of the reverse gate. 
     SUMMARY OF THE INVENTION 
     The inventors of preferred embodiments of the present invention described and claimed in the present application conducted an extensive study and research regarding a jet propelled watercraft, such as the one described above, and in doing so, discovered and first recognized new unique challenges and previously unrecognized possibilities for improvements as described in greater detail below. 
     With the jet propelled watercraft according to US Patent Application Publication No. 2013/0344754, the second accelerator operator (reverse gate operator) is not mechanically coupled to the reverse gate and therefore a large force is not required to operate the second accelerator operator. There is thus a possibility for an operator to operate the second accelerator operator unconsciously when the engine is being stopped. When the engine is started in a state where the second accelerator operator is operated, the jet propelled watercraft may be driven in reverse immediately after the engine is started. 
     In order to overcome the previously unrecognized and unsolved challenges described above, a preferred embodiment of the present invention provides a jet propelled watercraft including a body, a prime mover, a jet pump driven by the prime mover and jetting water from a jet port, a reverse gate changing a direction of the jet flow jetted from the jet pump, a shift actuator capable of moving the reverse gate, a reverse gate operator operated by an operator to set a position of the reverse gate, a reverse gate operation detector detecting an operation state of the reverse gate operator, and a controller configured or programmed to determine, in accordance with the operation state of the reverse gate operator detected by the reverse gate operation detector, whether or not the reverse gate operator is being operated and to prohibit startup of the prime mover when it is determined that the reverse gate operator is being operated. The shift actuator is capable of moving the reverse gate to a plurality of shift positions including at least a forward drive position, at which the direction of the jet flow is toward the rear of the body, and a reverse drive position, at which the direction of the jet flow is toward the front of the body. 
     With this arrangement, the startup of the prime mover is prohibited when it is determined that the reverse gate operator is being operated and therefore the body is prevented from being driven in reverse immediately after the startup of the prime mover. 
     In a preferred embodiment of the present invention, the reverse gate operation detector is configured to detect an operation amount of the reverse gate operator and the controller is configured or programmed to determine that the reverse gate operator is being operated when the operation amount of the reverse gate operator detected by the reverse gate operation detector is not less than a predetermined threshold. Whether or not the reverse gate operator is being operated is thus determined appropriately, and the prime mover startup prohibition when the reverse gate operator is being operated is performed appropriately. 
     In a preferred embodiment of the present invention, the reverse gate operation detector is configured to output a reverse gate position command signal in accordance with operation of the reverse gate operator and the controller is configured or programmed to determine that the reverse gate operator is being operated when the reverse gate position command signal is being output. With this arrangement, whether or not the reverse gate operator is being operated is determined based on whether or not the reverse gate position command signal is being output. The startup of the prime mover is thus prohibited under circumstances where there is a possibility for the reverse gate position to be changed in response to the position command signal. The startup of the prime mover is thus prohibited appropriately. 
     In a preferred embodiment of the present invention, the reverse gate operator includes a lever that is rotatingly operated by the operator. 
     In a preferred embodiment of the present invention, the reverse gate operation detector is configured to detect an operation angle of the lever and the controller is configured or programmed to determine that the reverse gate operator is being operated when the operation angle of the lever detected by the reverse gate operation detector is not less than a predetermined threshold. With this arrangement, the startup of the prime mover is prohibited when the operation angle of the lever is not less than the threshold. The startup of the prime mover is thus prohibited appropriately. 
     In a preferred embodiment of the present invention, the prime mover is an engine, a starter motor configured to start the engine is further included, and the controller is configured or programmed to determine, in accordance with the operation state of the reverse gate operator detected by the reverse gate operation detector, whether or not the reverse gate operator is being operated, and configured or programmed so as not to drive the starter motor when it is determined that the reverse gate operator is being operated. As a result, the starting of the engine in a state where the reverse gate operator is being operated is avoided. 
     A preferred embodiment of the present invention further includes an accelerator operator operated by the operator to set a rotational speed of the prime mover and an accelerator operation detector detecting an operation state of the accelerator operator, and the controller is configured or programmed to determine, in accordance with the operation state of the accelerator operator detected by the accelerator operation detector, whether or not the accelerator operator is being operated and to prohibit the startup of the prime mover when it is determined that the accelerator operator is being operated. 
     With this arrangement, the startup of the prime mover is prohibited when it is determined that the accelerator operator is being operated and therefore the rotational speed of the prime mover is suppressed to be low immediately after startup. Application of a large propulsive force to the body immediately after the startup of the prime mover is thus avoided. 
     In a preferred embodiment of the present invention, the reverse gate operation detector is configured to detect an operation amount of the reverse gate operator, the accelerator operation detector is configured to detect an operation amount of the accelerator operator, and the controller is configured or programmed to determine that the reverse gate operator is being operated when the operation amount of the reverse gate operator detected by the reverse gate operation detector is not less than a predetermined first threshold and to determine that the accelerator operator is being operated when the operation amount of the accelerator operator detected by the accelerator operation detector is not less than a predetermined second threshold differing from the first threshold. 
     With this arrangement, whether or not the accelerator operator is being operated and whether or not the reverse gate operator is being operated is appropriately determined respectively, and the prime mover startup prohibition when these operators are being operated is performed appropriately. 
     In a preferred embodiment of the present invention, the reverse gate operator includes a reverse lever that is rotatingly operated by the operator, the accelerator operator includes an accelerator lever that is rotatingly operated by the operator, the operation amount of the reverse gate operator is an operation angle of the reverse lever, and the operation amount of the accelerator operator is an operation angle of the accelerator lever. 
     With this arrangement, the operation states of the accelerator lever and the reverse lever are determined appropriately and therefore the prime mover startup prohibition when these are being operated are performed appropriately. 
     In a preferred embodiment of the present invention, the reverse gate operator is configured to receive a setting of the rotational speed of the prime mover by the operator, and the rotational speed of the prime mover corresponding to the first threshold and the rotational speed of the prime mover corresponding to the second threshold are equal or substantially equal. With this arrangement, operations of the reverse gate operator and the accelerator operator are determined based on the rotational speed of the prime mover. The operations of the reverse gate operator and the accelerator operator is thus determined from a standpoint of the magnitude of a propulsive force generated when the prime mover is started up. The prime mover start prohibition is controlled more appropriately. 
     In a preferred embodiment of the present invention, the reverse gate operator is configured to receive a setting of the rotational speed of the prime mover by the operator, and the rotational speed of the prime mover corresponding to the first threshold and the rotational speed of the prime mover corresponding to the second threshold differ. With this arrangement, the prime mover rotational speed that serves as a basis for determining operation differs between the reverse gate operator and the accelerator operator. The operations of the reverse gate operator and the accelerator operator is thus determined from a standpoint of the respective magnitudes of a forward drive propulsive force and a reverse drive propulsive force generated when the prime mover is started up. The prime mover startup prohibition is thus controlled even more appropriately. 
     In a preferred embodiment of the present invention, the reverse gate operator is configured to receive a setting of the rotational speed of the prime mover by the operator. With this arrangement, by prohibiting the startup of the prime mover in a state where the reverse gate operator is being operated, generation of a large propulsive force is avoided when the prime mover is started up. 
     In a preferred embodiment of the present invention, the shift actuator is configured to move the reverse gate to the forward drive position, the reverse drive position, and a neutral position between the forward drive position and the reverse drive position, and the controller is configured or programmed to control the shift actuator to move the reverse gate to the neutral position when the prime mover is started up. 
     With this arrangement, if in the process of starting up the prime mover, the reverse gate is at the forward drive position or the reverse drive position, the reverse gate is moved to the neutral position when the prime mover is started up. The body is thus prevented from being driven forward or in reverse immediately after the startup of the prime mover. 
     Further with this arrangement, even if, due to some cause, the prime mover is started up in a state where the reverse gate operator is being operated, the body is prevented from being driven in reverse immediately after the startup of the prime mover. Also with this arrangement, even if, due to some cause, the prime mover is started up in a state where the accelerator operator is being operated, the body is prevented from being driven forward immediately after the startup of the prime mover. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a jet propelled watercraft according to a preferred embodiment of the present invention. 
         FIG. 2  is a perspective view of the arrangement of a vicinity of a handle of the jet propelled watercraft. 
         FIG. 3  is an enlarged perspective view of the arrangement of a vicinity of a right grip of the handle. 
         FIG. 4  is a schematic side view of the jet propelled watercraft in a state where a reverse gate is at a reverse drive position. 
         FIG. 5  is a schematic plan view of the arrangement of  FIG. 4 . 
         FIG. 6  is a schematic side view of the jet propelled watercraft in a state where the reverse gate is at a forward drive position. 
         FIG. 7  is a schematic side view of the jet propelled watercraft in a state where the reverse gate is at a neutral position. 
         FIG. 8  is a schematic view of rotation angle positions of a shift arm at a forward drive position, a neutral position, and a reverse drive position. 
         FIG. 9  is a block diagram for describing the electrical arrangement of the jet propelled watercraft. 
         FIG. 10A  is a characteristics diagram of a setting example of a throttle opening degree with respect to an accelerator operation amount. 
         FIG. 10B  is a characteristics diagram of another setting example of the throttle opening degree with respect to the accelerator operation amount. 
         FIG. 11  is a flowchart of a procedure of an example of an engine start control process executed by an ECU. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a schematic view of a jet propelled watercraft according to a preferred embodiment of the present invention. The jet propelled watercraft  1  is a small vessel used to travel on a body of water, such as a lake or sea, etc. The jet propelled watercraft  1  according to the present preferred embodiment is a personal watercraft (PWC), for example. 
     The jet propelled watercraft  1  includes a body  2 , an engine  3  as a prime mover disposed in an interior of the body  2 , and a jet propulsion device  4  mounted on a rear portion of the body  2 . The engine  3  and the jet propulsion device  4  constitute a propulsion generator that applies a propulsive force to the body  2 . 
     The body  2  includes a hull  5  that defines a watercraft bottom and a deck  6  disposed above the hull  5 . The engine  3  is disposed in a space defined between the hull  5  and the deck  6 . Further in the space is disposed a battery B 1  that supplies electric power to electrical equipment included in the jet propelled watercraft  1 . The engine  3  is disposed in front of the jet propulsion device  4 . 
     The engine  3  is an internal combustion engine that includes a crankshaft  3   a  rotatable around a rotation axis extending in a front/rear direction. The engine  3  includes an engine speed sensor  25  configured to detect a rotational speed of the engine  3 . The jet propulsion device  4  is driven by the engine  3 . The jet propulsion device  4  jets water, sucked into a watercraft interior (into the interior of the body  2 ) from the watercraft bottom, to a watercraft exterior (exterior of the body  2 ) to generate the propulsive force to propel the jet propelled watercraft  1  forward or in reverse. 
     A seat  7 , on which an operator sits, is disposed on the deck  6 . The seat  7  is disposed above the engine  3 . The seat  7  is disposed at a center in a width direction of the jet propelled watercraft  1 . A handle  8  is disposed in front of the seat  7 . The handle  8  is an operating member operated by the operator to change a direction of the body  2 . 
       FIG. 2  is a perspective view of the arrangement of a vicinity of the handle  8 . A display  9  is disposed in front of the handle  8 . The handle  8  includes a right grip  11  and a left grip  12 . A first accelerator operator (accelerator operator)  13  is rotatably mounted on the right grip  11 . A second accelerator operator (reverse gate operator)  14  is rotatably mounted on the left grip  12 . On the handle  8 , an operation box  15  is mounted at an inner side of the right grip  11 . A start switch  16  to start the engine and a stop switch  17  to stop the engine are provided at an inner side of the left grip  12  of the handle  8 . 
     The first accelerator operator  13  is mainly operated to drive the jet propelled watercraft  1  forward. In the present preferred embodiment, the first accelerator operator  13  preferably is a lever type that includes an accelerator lever. An amount of operation of the first accelerator operator  13  (operation angle of the accelerator lever; hereinafter referred to as the “first accelerator operation amount Am 1 ”) is detected by a first accelerator position sensor  18 . The first accelerator position sensor  18  is, for example, a potentiometer. The first accelerator position sensor  18  is an example of an accelerator operation detector that detects an operation state of the first accelerator operator  13 . 
     The second accelerator operator  14  is mainly operated to drive the jet propelled watercraft  1  in reverse or to reduce a forward speed of the jet propelled watercraft  1 . In the present preferred embodiment, the second accelerator operator  14  preferably is a lever type that includes a reverse lever. An amount of operation of the second accelerator operator  14  (operation angle of the reverse lever; hereinafter referred to as the “second accelerator operation amount Am 2 ”) is detected by a second accelerator position sensor  19 . The second accelerator position sensor  19  is, for example, a potentiometer. The second accelerator position sensor  19  is an example of a reverse gate operation detector that detects an operation state of the second accelerator operator  14 . 
       FIG. 3  is an enlarged perspective view of the arrangement of a vicinity of the right grip of the handle. A low-speed travel mode switch  21 , a constant-speed travel mode switch  22 , an acceleration fine adjustment switch  23 , and a deceleration fine adjustment switch  24  are provided in the operation box  15 . The switches  21  to  24  are disposed in a region enabling operation with a right thumb of the operator in a state where he/she holds the right grip  11  with the right hand. 
     The jet propelled watercraft  1  can be made to travel in any of a plurality of travel modes. The plurality of travel modes include an ordinary travel mode, a low-speed travel mode, and a constant-speed travel mode, for example. The ordinary travel mode is a travel mode (first mode) in which the jet propelled watercraft  1  travels at a speed that is in accordance with operations of the first accelerator operator  13  and the second accelerator operator  14 . The low-speed travel mode is a mode (second mode) in which the jet propelled watercraft  1  travels at a predetermined low speed. The constant-speed travel mode is a mode in which the jet propelled watercraft  1  travels at the speed at the point at which the constant-speed travel mode switch  22  is operated. 
     The low-speed travel mode switch  21  is a switch configured to set the travel mode to the low-speed travel mode and is an example of a mode switching signal output that outputs a mode switching signal to switch from the ordinary travel mode to the low-speed travel mode. The fine adjustment switches  23  and  24  are switches configured to finely adjust the speed of the jet propelled watercraft  1  in the low-speed travel mode. The constant-speed travel mode switch  22  is a switch configured to set the travel mode to the constant-speed travel mode. 
     As shown in  FIG. 1 , the jet propulsion device  4  includes a jet pump  32 , by which water of the watercraft exterior that is sucked in from the watercraft bottom is jetted rearward, and a reverse gate  33 , which changes a direction of a jet flow jetted from the jet pump  32 . 
     The jet pump  32  includes an intake  41  through which the watercraft exterior water is sucked in, an outlet  42  from which the water sucked in from the intake  41  is jetted rearward, and a flow passage  43  guiding the water sucked into the intake  41  to the outlet  42 . The jet pump  32  further includes an impeller  44  (rotor vane) and a stator vane  45  that are disposed in the flow passage  43 , a driveshaft  46  coupled to the impeller  44 , a nozzle  47  defining the outlet  42 , and a deflector  48  inclining the direction of the jet flow, jetted rearward from the nozzle  47 , to the right and left. 
     The intake  41  is opened at the watercraft bottom and the outlet  42  is opened rearward further to the rear than the intake  41 . The driveshaft  46  extends in the front/rear direction. A front end portion of the driveshaft  46  is disposed inside the watercraft and a rear end portion of the driveshaft  46  is disposed in the flow passage  43 . The front end portion of the driveshaft  46  is coupled to the crankshaft  3   a  of the engine  3  via a coupling  49 . The impeller  44  is coupled to the driveshaft  46 . The stator vane  45  is disposed rearward of the impeller  44 . The nozzle  47  is disposed rearward of the stator vane  45 . The impeller  44  is rotatable around a central axis of the driveshaft  46  with respect to the flow passage  43 . The stator vane  45  is fixed with respect to the flow passage  43 . The nozzle  47  is fixed to the body  2 . 
     The engine  3  drives the impeller  44 , together with the driveshaft  46 , around the central axis of the driveshaft  46 . When the impeller  44  is driven to rotate, water is sucked into the flow passage  43  from the intake  41  and the water sucked into the flow passage  43  is fed from the impeller  44  to the stator vane  45 . By the water fed by the impeller  44  passing through the stator vane  45 , torsion of water flow generated by rotation of the impeller  44  is reduced and the water flow is straightened. The flow-straightened water is thus fed from the stator vane  45  to the nozzle  47 . The nozzle  47  has a tubular form extending in the front/rear direction and the outlet  42  is formed by a rear end portion of the nozzle  47 . The water fed to the nozzle  47  is thus jetted rearward from the rear end portion of the nozzle  47 . 
       FIG. 4  is a schematic side view showing the arrangement of a vicinity of the nozzle  47  in enlarged manner.  FIG. 5  is a schematic plan view of the arrangement of  FIG. 4 . The deflector  48  is disposed rearward of the nozzle  47 . The deflector  48  is supported by the nozzle  47  in a manner enabling rotation in a right/left direction. The deflector  48  has a hollow tube shape. The outlet  42  of the nozzle  47  is disposed inside the deflector  48 . The deflector  48  defines a jet port  31  that is opened rearward. The jet port  31  is disposed rearward of the outlet  42 . The water that is jetted rearward from the nozzle  47  passes through an interior of the deflector  48  and is jetted from the jet port  31 . A jetting direction of the water is in accordance with a right/left direction angle of the deflector  48 . 
     The reverse gate  33  is supported by the nozzle  47  in a manner enabling rotation around an up/down rotation axis Ag extending in the right/left direction. For the sake of description, in the following, front, rear, up, and down with respect to the reverse gate  33  shall refer to front, rear, up, and down as defined in a state where the reverse gate  33  is at the position shown in  FIG. 4  and  FIG. 5 . The reverse gate  33  includes a rear wall  51  as an opening/closing portion that opens/closes the jet port  31  of the deflector  48 , a left side wall  52  extending frontward from a left side portion of the rear wall  51 , and a right side wall  53  extending frontward from a right side portion of the rear wall  51 . The left side wall  52  and the right side wall  53  have fan shapes spreading toward the rear in side view. A left opening  54  that is opened obliquely forward to the left is located near a rear end of the left side wall  52 . A right opening  55  that is opened obliquely forward to the right is located near a rear end of the right side wall  53 . The left opening  54  and the right opening  55  are right/left symmetrical to a vertical plane passing through a right/left center of the reverse gate  33 . 
     A pair of right and left support brackets  61  are mounted to the nozzle  47 . Front end portions of the respective side walls  52  and  53  of the reverse gate  33  are supported by the support brackets  61  via bolts  62 , for example. The bolts  62  are inserted through the side walls  52  and  53  of the reverse gate  33  and screwed to the support brackets  61 . The bolts  62  are respectively disposed along the up/down rotation axis Ag and at the right and left of the nozzle  47 . The reverse gate  33  is thus enabled to rotate around the up/down rotation axis Ag with respect to the nozzle  47 . 
     The front end portions of the respective side walls  52  and  53  include curved end surfaces  33   a  including portions that are arcuate-shaped around the up/down rotation axis Ag. The front end portions of the respective side walls  52  and  53  further include first rectilinear end surfaces  33   b  connected to upper ends of the curved end surfaces  33   a  and extending substantially upward and second rectilinear end surfaces  33   c  connected to lower ends of the curved end surfaces  33   a  and extending substantially downward. 
     The reverse gate  33  is capable of moving to a reverse drive position shown in  FIG. 4  and  FIG. 5 , a forward drive position shown in  FIG. 6 , and a neutral position shown in  FIG. 7  by rotating around the up/down rotation axis Ag. The forward drive position is a position at which the jet port  31  is not covered at all by the rear wall  51  of the reverse gate  33  in a rear view viewed along the jetting direction of the water jetted from the jet port  31  of the deflector  48 . The reverse drive position is a position at which the entire jet port  31  of the deflector  48  is covered by the rear wall  51  of the reverse gate  33  in the rear view. The neutral position is a predetermined position between the forward drive position and the reverse drive position and is a position at which a portion of the jet port  31  of the deflector  48  is covered by the rear wall  51  of the reverse gate  33  in the rear view. 
     In the state where the reverse gate  33  is disposed at the forward drive position (see  FIG. 6 ), the jet port  31  of the deflector  48  is not covered by the reverse gate  33  and therefore the water jetted rearward from the outlet  42  of the nozzle  47  thus passes through the interior of the deflector  48  and is jetted rearward from the jet port  31 . A thrust in a forward drive direction that drives the body  2  forward is thus generated. 
     In the state where the reverse gate  33  is disposed at the reverse drive position (see  FIG. 4 ), the entire jet port  31  of the deflector  48  is covered by the reverse gate  33 . The water jetted rearward from the jet port  31  thus collides against an inner surface of the reverse gate  33  and is thereafter jetted obliquely forward to the left and obliquely forward to the right from the left opening  54  and the right opening  55 . The reverse gate  33  thus changes the direction of the water, jetted rearward from the jet port  31 , toward the front. A thrust in a reverse drive direction that drives the body  2  in reverse is thus generated. 
     When the reverse gate  33  is disposed at the neutral position (see  FIG. 7 ), a portion of the jet port  31  of the deflector  48  is covered by the reverse gate  33 . Therefore, while a portion of the water jetted from the jet port  31  is jetted rearward, another portion of the water jetted from the jet port  31  is jetted obliquely forward to the left and obliquely forward to the right from the left opening  54  and the right opening  55 . A thrust in the forward drive direction and a thrust in the reverse drive direction are thus generated. The neutral position is set, for example, at a position at which the forward drive direction thrust and the reverse drive direction thrust are equal or substantially equal. 
     Each support bracket  61  is provided with a stopper  63  which the reverse gate  33  is pressed against at the forward drive position (see  FIG. 6 ) and the reverse drive position (see  FIG. 4 ). The stopper  63  has a rectangular or substantially rectangular plate shape that is long in the up/down direction in side view. An upper end surface of the stopper  63  is a first stopper surface  63   a  and a rear end surface of the stopper is a second stopper surface  63   b.    
     As shown in  FIG. 6 , when the reverse gate  33  is at the forward drive position, the first rectilinear end surfaces  33   b  of the respective side walls  52  and  53  of the reverse gate  33  are pressed against the first stopper surfaces  63   a  of the stoppers  63 . As shown in  FIG. 4  and  FIG. 5 , when the reverse gate  33  is at the reverse drive position, the second rectilinear end surfaces  33   c  of the respective side walls  52  and  53  of the reverse gate  33  are pressed against the second stopper surfaces  63   b  of the stoppers  63 . As shown in  FIG. 7 , when the reverse gate  33  is at the neutral position, the reverse gate  33  is not pressed against the stoppers  63 . 
     The jet propelled watercraft  1  includes a deflector moving mechanism (not shown) that rotates the deflector  48  to the right or left in accordance with an operation amount (steering angle) of the handle  8 . The deflector moving mechanism mechanically couples the handle  8  and the deflector  48 . The deflector moving mechanism includes, for example, a push-pull cable that transmits an actuation of the handle  8  to the deflector  48 . The deflector moving mechanism may be an electrically driven moving mechanism that includes an electric motor, for example. A straight drive position of the handle  8  is associated with a straight drive position of the deflector  48 . When the handle  8  is operated, the deflector  48  is rotated to the left or to the right by the deflector moving mechanism. The jetting direction of the water from the jet port  31  is thus changed to the right or left. 
     The jet propelled watercraft  1  further includes a reverse gate moving mechanism  64  (see  FIG. 1 ,  FIG. 4 ,  FIG. 6 , and  FIG. 7 ) that rotates the reverse gate  33  up and down based on operation of the first accelerator operator  13  and the second accelerator operator  14 . In the present preferred embodiment, the reverse gate moving mechanism  64  includes a shift actuator  65 , a shift arm  66  rotated by the shift actuator  65 , and a link  67  coupling the shift arm  66  and the reverse gate  33 . In the present preferred embodiment, the shift actuator  65  preferably is an electric motor, for example. 
     The link  67  is pushed or pulled when the shift arm  66  is rotated by the shift actuator  65 . The reverse gate  33  is thus rotated around the up/down rotation axis Ag. A shift position of the reverse gate  33  (hereinafter referred to simply as the “shift position”) is detected by a shift position sensor  68 . The shift position sensor  68  is an example of a shift position detector or a shift state detector that detects the shift position or a shift state. In the present preferred embodiment, the shift position sensor  68  preferably is a potentiometer that detects a rotation angle (rotation amount) of the shift arm  66  from a reference position set in advance. 
       FIG. 8  is a schematic view of rotation angle positions of the shift arm  66  at the forward drive position, the neutral position, and the reverse drive position. In the present preferred embodiment, the reference position P of the shift arm  66  is a position at which the shift arm  66  is perpendicular or substantially perpendicular to a horizontal plane of the body  2 . A position F, at which the shift arm  66  is rotated in a counterclockwise direction by just a predetermined angle θ F  from the reference position P, indicates the rotation angle position of the shift arm  66  corresponding to the forward drive position of the reverse gate  33 . A position R, at which the shift arm  66  is rotated in a clockwise direction by just a predetermined angle θ R  from the reference position P, indicates the rotation angle position of the shift arm  66  corresponding to the reverse drive position of the reverse gate  33 . A position N, at which the shift arm  66  is rotated in the clockwise direction by just a predetermined angle θ N  from the reference position P, indicates the rotation angle position of the shift arm  66  corresponding to the neutral position of the reverse gate  33 . 
       FIG. 9  is a block diagram for describing the electrical configuration of the jet propelled watercraft  1 . The engine  3 , the shift actuator  65 , the display  9 , etc., are controlled by an ECU  70  (electronic controller) the defines a controller. The engine  3  includes a starter motor  71 , an ignition coil  72 , an injector  73 , and a throttle actuator  74 . 
     Switches, including the start switch  16 , the stop switch  17 , the low-speed travel mode switch  21 , the constant-speed travel mode switch  22 , the acceleration fine adjustment switch  23 , and the deceleration fine adjustment switch  24 , are connected to the ECU  70 . Further, sensors, including the first accelerator position sensor  18 , the second accelerator position sensor  19 , the engine speed sensor  25 , and the shift position sensor  68 , are connected to the ECU  70 . 
     Further, the display  9 , and actuators, such as the starter motor  71 , the ignition coil  72 , the injector  73 , the throttle actuator  74 , the shift actuator  65 , etc., are connected to the ECU  70 . The starter motor  71  is configured to perform cranking of the engine  3 . The injector  73  is configured to inject fuel into an air intake path of the engine  3 . The throttle actuator  74  is configured to drive a throttle valve (not shown) of the engine  3  to adjust an amount of air supplied to the air intake path of the engine  3 . The ignition coil  72  is configured to raise a voltage applied to a spark plug (not shown). 
     The ECU  70  includes a microcomputer (not shown) and a storage device such as a memory  81  storing a program thereof, etc. The ECU  70  further includes drive circuits (not shown) of the starter motor  71 , the throttle actuator  74 , and the shift actuator  65 . Information expressing the angles θ F , θ R , and θ N  shown in  FIG. 8  are stored in the storage device  81 . 
     The ECU  70  calculates a first throttle opening degree Θ 1  corresponding to the first accelerator operation amount Am 1  detected by the first accelerator position sensor  18 . The ECU  70  further calculates a second throttle opening degree Θ 2  corresponding to the second accelerator operation amount Am 2  detected by the second accelerator position sensor  19 . 
     A straight line L 1  in  FIG. 10A  indicates a setting example of the first throttle opening degree Θ 1  with respect to the first accelerator operation amount Am 1 . A straight line L 2  in  FIG. 10A  indicates a setting example of the second throttle opening degree Θ 2  with respect to the second accelerator operation amount Am 2 . The first throttle opening degree Θ 1  is set so as to increase linearly as the first accelerator operation amount Am 1  increases. Similarly, the second throttle opening degree Θ 2  is set so as to increase linearly as the second accelerator operation amount Am 2  increases. However, with the present preferred embodiment, a rate of change of the second throttle opening degree Θ 2  with respect to the second accelerator operation amount Am 2  (slope of the straight line L 2 ) is smaller than a rate of change of the first throttle opening degree Θ 1  with respect to the first accelerator operation amount Am 1  (slope of the straight line L 1 ). Therefore, when the first accelerator operation amount Am 1  and the second accelerator operation amount Am 2  are of the same value, the second throttle opening degree Θ 2  is less than the first throttle opening degree Θ 1 . 
     In the ordinary travel mode, the ECU  70  performs an ordinary rotational speed control process and an ordinary shift control process. In the ordinary rotational speed control process, the ECU  70  controls the throttle actuator  74  in accordance with the first throttle opening degree Θ 1  and the second throttle opening degree Θ 2  to control the engine speed. Specifically, when the shift position is the forward drive position, the ECU  70  controls the throttle opening degree, for example, in accordance with a difference between the first throttle opening degree Θ 1  and the second throttle opening degree Θ 2  (hereinafter referred to as the “throttle opening degree difference (Θ 1 −Θ 2 )”). When the shift position is the reverse drive position or the neutral position, the ECU  70  controls the throttle opening degree, for example in accordance with the throttle opening degree Θ 2 . 
     The ECU  70  may perform the ordinary rotational speed control process by the same method as a rotational speed control method disclosed in United States Patent Application Publication No. 2013/0344754. The entire contents of US Patent Application Publication No. 2013/0344754 are incorporated herein by reference. 
     In the ordinary shift control process, the ECU  70  controls the shift actuator  65  in accordance with the first throttle opening degree Θ 1 , the second throttle opening degree Θ 2 , and the engine speed V detected by the engine speed sensor  25  to control the shift position. 
     When for example, in a case where the shift position is the forward drive position, the throttle opening degree difference (Θ 1 −Θ 2 ) is less than a predetermined value, the second accelerator operator  14  is operated, and the engine speed V is greater than a predetermined speed, the ECU  70  switches the shift position to the neutral position. Specifically, the ECU  70  sets a target shift position to the neutral position and thereafter controls the shift actuator  65  to move the reverse gate  33  to the target shift position. The most recent target shift position is held in the storage  81 . The ECU  70  judges whether or not the reverse gate  33  has reached the target shift position. Specifically, the ECU  70  judges whether or not the rotation angle detected by the shift position sensor  68  has become equal to the angle, among the angles θ F , θ R  and θ N  stored in the storage  81 , corresponding to the target shift position. 
     When for example, in a case where the shift position is the forward drive position, the throttle opening degree difference (Θ 1 −Θ 2 ) is less than the predetermined value, the second accelerator operator  14  is operated, and the engine speed V is not more than the predetermined speed, the ECU  70  switches the shift position to the reverse drive position. Specifically, the ECU  70  sets the target shift position to the reverse drive position and thereafter controls the shift actuator  65  to move the reverse gate  33  to the target shift position. 
     When for example, in a case where the shift position is the neutral position, the engine speed V is less than the predetermined speed and the second accelerator operator  14  is operated, the ECU  70  switches the shift position to the reverse drive position. Specifically, the ECU  70  sets the target shift position to the reverse drive position and thereafter controls the shift actuator  65  to move the reverse gate  33  to the target shift position. 
     When for example, in a case where the shift position is the neutral position, the engine speed V is less than the predetermined speed, the second accelerator operator  14  is not operated, and the first accelerator operator  13  is operated, the ECU  70  switches the shift position to the forward drive position. Specifically, the ECU  70  sets the target shift position to the forward drive position and thereafter controls the shift actuator  65  to move the reverse gate  33  to the target shift position. 
     When for example, in a case where the shift position is the reverse drive position, the second accelerator operator  14  is not operated and the first accelerator operator  13  is operated, the ECU  70  switches the shift position to the forward drive position. Specifically, the ECU  70  sets the target shift position to the forward drive position and thereafter controls the shift actuator  65  to move the reverse gate  33  to the target shift position. 
     When for example, in a case where the shift position is the reverse drive position, a state where the second accelerator operator  14  and the first accelerator operator  13  are not operated is sustained for not less than a predetermined time, the ECU  70  switches the shift position to the neutral position. Specifically, the ECU  70  sets the target shift position to the neutral position and thereafter controls the shift actuator  65  to move the reverse gate  33  to the target shift position. 
     The reverse gate  33  is thus controlled in position in accordance with the operation of the second accelerator operator  14 . That is, the second accelerator operator  14  and the second accelerator position sensor  19  that detects the operation amount thereof constitute a shift switching signal output that outputs a shift switching signal. 
     The ECU  70  may perform the ordinary shift control process by the same method as a shift control method disclosed in United States Patent Application Publication No. 2013/0344754. 
       FIG. 11  is a flowchart of a procedure of an example of an engine start control process executed by the ECU  70 . 
     The ECU  70  determines whether or not the start switch  16  has been turned on in a state where the engine is stopped (step S 1 ). If the start switch  16  has not been turned on (step S 1 : NO), the ECU  70  returns to step S 1 . 
     If in step S 1 , it is determined that the start switch  16  has been turned on (step S 1 : YES), the ECU  70  determines whether or not the first accelerator operator  13  is being operated (step S 2 ). Specifically, the ECU  70  determines whether or not the first accelerator operation amount Am 1  detected by the first accelerator position sensor  18  is not less than a first threshold α 1 . The ECU  70  determines that the first accelerator operator  13  is being operated if the first accelerator operation amount Am 1  is not less than the first threshold al, and determines that the first accelerator operator  13  is not being operated if the first accelerator operation amount Am 1  is less than the first threshold α 1 . 
     If it is determined that the first accelerator operator  13  is not being operated (step S 2 : NO), the ECU  70  determines whether or not the second accelerator operator  14  is being operated (step S 3 ). Specifically, the ECU  70  determines whether or not the second accelerator operation amount Am 2  detected by the second accelerator position sensor  19  is not less than a second threshold α 2 . The ECU  70  determines that the second accelerator operator  14  is being operated if the second accelerator operation amount Am 2  is not less than the second threshold α 2 , and determines that the second accelerator operator  14  is not being operated if the second accelerator operation amount Am 2  is less than the second threshold α 2 . 
     With the present preferred embodiment, the second threshold α 2  is set to a value greater than the first threshold α 1  as shown in  FIG. 10A . Also with the present preferred embodiment, the first threshold α 1  and the second threshold α 2  are set so that a first throttle opening degree Θ 1  corresponding to the first threshold α 1  and a second throttle opening degree Θ 2  corresponding to the second threshold α 2  are of equal value (Θa). That is, the engine speed corresponding to the first threshold α 1  and the engine speed corresponding to the second threshold α 2  are equal or substantially equal to each other. 
     If it is determined that the second accelerator operator  14  is not being operated (step S 3 : NO), the ECU  70  performs an engine starting process (step S 4 ). Specifically, the ECU  70  drives the starter motor  71 , the ignition coil  72 , and the injector  73  and performs fuel supply control and ignition control to start the engine  3 . The ECU  70  then determines whether or not the engine  3  has been started (step S 5 ). Specifically, the ECU  70  determines the starting of the engine  3  based on whether or not the engine speed V detected by the engine speed sensor  25  is not less than a predetermined start determination threshold β 1 . That is, the ECU  70  determines that the engine  3  has been started if the engine speed V is not less than the start determination threshold β 1  and determines that the engine  3  has not been started if the engine speed V is less than the start determination threshold β 1 . If it is determined that the engine  3  has not been started (step S 5 : NO), the ECU  70  returns to step S 4  to perform the engine starting process. 
     If in step S 5 , it is determined that the engine  3  has been started (step S 5 : YES), the ECU  70  determines whether or not the shift position is the neutral position (step S 6 ). If the shift position is other than the neutral position (step S 6 : NO), the ECU  70  sets the target shift position to the neutral position and thereafter controls the shift actuator  65  to move the reverse gate  33  to the neutral position (step S 7 ). The ECU  70  then ends the engine start control process and starts control in the ordinary travel mode. 
     If in step S 6 , it is determined that the shift position is the neutral position (step S 6 : YES), the ECU  70  ends the engine start control process and starts control in the ordinary travel mode. 
     If in step S 2 , it is determined that the first accelerator operator  13  is being operated (step S 2 : YES), the ECU  70  returns to step S 1 . The ECU  70  also returns to step S 1  if in step S 3 , it is determined that the second accelerator operator  14  is being operated (step S 3 : YES). 
     If it is determined that the first accelerator operator  13  is being operated in step S 2  or it is determined that the second accelerator operator  14  is being operated in step S 3 , the ECU  70  may return to step S 1  upon displaying an error on the display  9 . 
     With the present preferred embodiment, even when the start switch  16  is turned on, the starting of the engine  3  is prohibited if it is determined that the first accelerator operator  13  is being operated (step S 2 ). Driving of the body  2  forward by the moving of the reverse gate  33  to the forward drive position immediately after the starting of the engine is thus prevented. Further, the rotational speed of the engine  3  immediately after the starting of the engine is suppressed to a low speed and application of a large propulsive force to the body  2  immediately after the starting of the engine is avoided. 
     With the present preferred embodiment, it is determined that the first accelerator operator  13  is being operated when the first accelerator operation amount Am 1  is not less than the first threshold α 1 . Whether or not the first accelerator operator  13  is being operated is thus determined appropriately, and accordingly, engine start prohibition when the first accelerator operator  13  is being operated is performed appropriately. 
     With the present preferred embodiment, the first accelerator operator  13  includes the accelerator lever. The first accelerator operation amount Am 1  corresponds to the operation angle of the accelerator lever. The operation state of the accelerator lever is thus determined appropriately and start prohibition of the engine  3  during accelerator lever operation is performed appropriately. More specifically, the starting of the engine  3  is prohibited when the operation angle of the accelerator lever is not less than the predetermined threshold. The starting of the engine  3  is thus prohibited appropriately. 
     With the present preferred embodiment, even when the start switch  16  is turned on, the starting of the engine  3  is prohibited if it is determined that the second accelerator operator  14  is being operated (step S 3 ). The driving of the body  2  in reverse by the moving of the reverse gate  33  to the reverse drive position immediately after engine start is thus prevented. Further, the rotational speed of the engine  3  is suppressed to be low immediately after engine start and application of a large propulsive force to the body  2  immediately after engine start is avoided. 
     With the present preferred embodiment, it is determined that the second accelerator operator  14  is being operated when the second accelerator operation amount Am 2  is not less than the second threshold α 2 . Whether or not the second accelerator operator  14  is being operated is thus determined appropriately, and accordingly, engine start prohibition when the second accelerator operator  14  is being operated is performed appropriately. 
     With the present preferred embodiment, the second accelerator operator  14  includes the reverse lever. The second accelerator operation amount Am 2  corresponds to the operation angle of the reverse lever. The operation state of the reverse lever is thus determined appropriately and start prohibition of the engine  3  during reverse lever operation is performed appropriately. More specifically, the starting of the engine  3  is prohibited when the operation angle of the reverse lever is not less than the predetermined threshold. The starting of the engine  3  is thus prohibited appropriately. 
     With the present preferred embodiment, the first throttle opening degree Θ 1  corresponding to the first threshold α 1  and the second throttle opening degree Θ 2  corresponding to the second threshold α 2  are equal or substantially equal. That is, the rotational speed of the engine  3  corresponding to the first threshold α 1  and the rotational speed of the engine  3  corresponding to the second threshold α 2  are equal. Operations of the first accelerator operator  13  and the second accelerator operator  14  are thus determined based on the rotational speed of the engine  3 . The operations of the first accelerator operator  13  and the second accelerator operator  14  is thus determined from a standpoint of the magnitude of the propulsive force generated when the engine  3  is started. The start prohibition of the engine  3  is thus controlled more appropriately. 
     If, immediately after engine start, the shift position is determined to be other than the neutral position, the reverse gate  33  is moved to the neutral position (steps S 6  and S 7 ). The reverse gate  33  is thus moved to the neutral position immediately after engine start even if the shift position is at the forward drive position or the reverse drive position at engine start, and the body  2  is thus suppressed from being driven forward or in reverse immediately after engine start. 
     Even if, due to some cause, the engine  3  is started in a state where at least one of either the first accelerator operator  13  or the second accelerator operator  14  is being operated, the body  2  is suppressed from being driven forward or in reverse immediately after engine start. For example, if the first or second accelerator position sensor  18  or  19  is malfunctioning, the determination of step S 2  or S 3  will not be performed correctly and the engine  3  may thus be started in a state where at least one of either the first or second accelerator operator  13  or  14  is being operated. Even in such a case, the reverse gate  33  is moved to the neutral position immediately after engine start and therefore the driving of the body  2  forward or in reverse immediately after engine start is avoided. 
     When a shift control is performed in the state that a rotation speed of the engine  3  is high, resistance of the water to be applied to reverse gate  33  becomes big. 
     There is thus a possibility that a big load is applied to a shift actuator  65 , or that the shift control is not performed normally. 
     If the shift control is permitted only when a rotation speed of the engine  3  is around an idling rotation speed, a responsiveness is deteriorated in at the time of the immediate acceleration after change from a reverse drive position to a forward drive position when the body is driven in reverse. 
     Therefore, ECU  70  may perform a speed limit control to limit a rotation speed of the engine  3  in a predetermined range during the shift control is being performed. For example, the predetermined range is set within the range of the rotation speed that is not less than the idling rotation speed and does not interfere with the shift control. 
     Although a preferred embodiment of the present invention has been described above, the present invention may be implemented in yet other preferred embodiments. 
     For example, with the preferred embodiments described above, the first threshold α 1  and the second threshold α 2  are preferably set so that the first throttle opening degree Θ 1  corresponding to the first threshold α 1  and the second throttle opening degree Θ 2  corresponding to the second threshold α 2  are of equal value (Θa). However, the first threshold α 1  and the second threshold α 2  may be set so that the first throttle opening degree Θ 1  corresponding to the first threshold α 1  and the second throttle opening degree Θ 2  corresponding to the second threshold α 2  take on different values. In this case, the engine speed that serves as a basis for determining operation differs between the first accelerator operator  13  and the second accelerator operator  14 . The operations of the first accelerator operator  13  and the second accelerator operator  14  is thus determined from a standpoint of the respective magnitudes of the forward drive propulsive force and the reverse drive propulsive force generated when the engine  3  is started. The start prohibition of the engine  3  is thus controlled even more appropriately. 
     Also, with the preferred embodiments described above, the rate of change of the second throttle opening degree Θ 2  with respect to the second accelerator operation amount Am 2  preferably is set to be smaller than the rate of change of the first throttle opening degree Θ 1  with respect to the first accelerator operation amount Am 1  as shown in  FIG. 10A . However, as shown in  FIG. 10B , the rate of change of the second throttle opening degree Θ 2  with respect to the second accelerator operation amount Am 2  (slope of the straight line L 2  in  FIG. 10B ) may be set to be equal to the rate of change of the first throttle opening degree Θ 1  with respect to the first accelerator operation amount Am 1  (slope of the straight line L 1  in  FIG. 10B ). In this case, the first threshold α 1  and the second threshold α 2  may be set to the same value as shown in  FIG. 10B . When the first threshold al and the second threshold α 2  are set to the same value, the first throttle opening degree Θ 1  corresponding to the first threshold α 1  and the second throttle opening degree Θ 2  corresponding to the second threshold α 2  take on the same value ( 8   b ). 
     With the preferred embodiments described above, in the ordinary travel mode, the ECU  70  performs the ordinary engine speed control process and the ordinary shift control process in accordance with the operation amount of the first accelerator operator  13 , the operation amount of the second accelerator operator (reverse gate operator)  14 , and the engine speed. However, in the ordinary travel mode, the ECU  70  may control the engine speed in accordance with the operation of the first accelerator operator  13  and perform shift control in accordance with the operation of the second accelerator operator  14 . That is, the second accelerator operator  14  may be used just to switch the shift position. 
     Although with the preferred embodiments described above, the second accelerator operator  14  preferably is a lever type, it may instead be of a grip type or may be a toggle switch or a button switch. Also, although with the preferred embodiments described above, the first accelerator operator  13  preferably is a lever type, it may instead be of a grip type. 
     If the second accelerator operator  14  is a switch, such as a toggle switch or button switch, etc., the second accelerator operator  14  constitutes a reverse gate operation detector that outputs a reverse gate position command signal in accordance with the operation of the second accelerator operator  14 . In this case, the ECU  70  determines that the second accelerator operator  14  is being operated when, for example, the reverse gate position signal is being output by the second accelerator operator  14 . That is, whether or not the second accelerator operator  14  is being operated is determined based on whether or not the reverse gate position command signal is output. The starting of the engine  3  is thus prohibited under circumstances where there is a possibility for the reverse gate position to be changed in response to the position command signal. The starting of the engine  3  is thus prohibited appropriately. 
     With the preferred embodiments described above, the shift position of the reverse gate  33  preferably is detected by the shift position sensor  68  that detects the rotation angle of the shift arm  66 . However, the shift position may be detected by a plurality of limit switches. 
     Although with the preferred embodiments described above, the shift actuator  65  preferably is an electric motor, a hydraulic actuator may be used instead. 
     Although with the preferred embodiments described above, the case where the prime mover preferably is the engine  3  was described, the prime mover may be an electric motor instead. In this case, the electric motor is started up as the prime mover in step S 4  of  FIG. 11 . In step S 5  of  FIG. 11 , it is judged whether or not the electric motor has been started up. 
     Although with the preferred embodiments described above, the engine  3 , the shift actuator  65 , the display  9 , etc., preferably are controlled by a single ECU  70 , these may be controlled by a plurality of ECUs instead. 
     Also, although with the preferred embodiments described above, the case where the jet propelled watercraft preferably is a personal watercraft was described, the present invention may be applied to a jet propelled watercraft of another form, such as a jet boat, a sport boat, etc. 
     The present application corresponds to Japanese Patent Application No. 2014-162715 filed on Aug. 8, 2014 in the Japan Patent Office, and the entire disclosure of this application is incorporated herein by reference. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.