CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 12/703,297 filed in the United States Patent Office on Feb. 10, 2010, now U.S. Pat. No 8,182,396 the full disclosure of which is incorporated herein by reference and priority to which is claimed. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to electronic shift and throttle systems and, in particular, to delaying shift and throttle functions based on engine speed. 
     2. Description of the Related Art 
     Vehicles such as marine vessels are often provided with electronic shift and throttle systems. These systems typically allow an operator to control the shift and throttle functions of a propulsion unit using a control lever which is pivotally mounted on a control head. The control lever is moveable between a forward wide open throttle (forward WOT) position and a reverse wide open throttle (reverse WOT) position, through a neutral position. A controller reads the position of the control lever as the control lever moves through its operational range. The controller sends shift commands and throttle commands which drive a shift actuator and a throttle actuator based on the position of the control lever. 
     For example, U.S. Pat. No. 7,330,782 issued on Feb. 12, 2008 to Graham et al. and the full disclosure of which is incorporated herein by reference, discloses an electronic shift and throttle system in which a position sensor is used to sense the position of a control lever. The position sensor is electrically connected to an electronic control unit (ECU) and sends an electrical signal to the ECU. The ECU is able to determine the position of the control lever based on the voltage level of the electrical signal received from the position sensor. The ECU then determines the positions to which the output shafts of the shift actuator and the throttle actuator should be set. 
     Each of the output shafts is also coupled to a corresponding position sensor. Electrical signals sent by these position sensors may be used to determine the positions of the output shafts. This feedback may be used to govern the ECU. This is beneficial because variances and play between components used to link throttle actuators to throttles make it desirable to calibrate throttle controls. Calibrated throttle controls allow an operator to delay shift and throttle functions based on engine speed in a marine vessel. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved method and system for delaying shift and throttle commands based on engine speed in a marine vessel. 
     There is accordingly provided a method for delaying shift and throttle commands based on engine speed. The method comprises establishing a predetermined threshold engine speed. Shift and throttle commands are calculated based on the position of a joystick which allows an operator to manually control shift and throttle functions. Execution of the shift and throttle commands is delayed if the engine speed is above the predetermined maximum threshold engine speed. 
     In one embodiment, a first threshold engine speed and a second engine threshold speed are established. The first threshold engine speed is greater than the second engine threshold speed. For example, the first threshold engine speed may be 1,500 RPM while the second threshold engine speed may be 800 RPM. The throttle actuator is moved to an idle position to decrease the engine speed until the engine speed falls below the first threshold engine speed. The shift actuator is moved to a neutral position after the engine speed falls below the first predetermined threshold engine speed. Execution of the throttle command is delayed until after the shift actuator is moved to the neutral position. Execution of the shift command is delayed until after the execution of the throttle command and the engine speed rises above the second predetermined threshold engine speed. 
     Also provided is an electronic shift and throttle system for delaying shift and throttle commands based on the speed of an engine. The system comprises a sensor for sensing the speed of the engine. There is a shift actuator for shifting between a forward gear and a reverse gear, through a neutral gear. There is also a throttle actuator for moving a throttle between an idle position and a wide open throttle position. A control head includes a joystick for manually controlling shift and throttle functions of the engines. The joystick is moveable through a range of positions. An engine control unit calculates a shift command and throttle command based on a position of the joystick. An engine servo module delays execution of the shift command if the speed of the engine is above a first predetermined threshold engine speed. In particular, the engine servo module commands the throttle actuator to move the throttle to the idle position to decrease engine speed and delays execution of the shift command until after the engine speed falls below the first threshold engine speed. 
     In one embodiment, the engine servo module commands the throttle actuator to move the throttle actuator towards the wide open position throttle position, to increase the engine speed, after the engine speed falls below the first predetermined threshold speed. The engine servo module also commands the shift actuator to shift to the neutral gear after engine speed falls below the first predetermined threshold engine speed. The engine servo module the delays the execution of the throttle command until after the shift actuator shifts to neutral the neutral gear. The engine servo module delays execution of the shift command until the engine speed rises above a second predetermined threshold engine speed. 
     The present invention provides an improved method for delaying shift and throttle commands based on engine speed that allows an operator to quickly shift from forward high throttle to reverse high throttle or vice versa without overstressing the gear box and while helping to prevent the engine from stalling under the high opposite force of the propeller. 
    
    
     
       BRIEF DESCRIPTIONS OF DRAWINGS 
       The invention will be more readily understood from the following description of the embodiments thereof given, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a marine vessel provided with a plurality of propulsion units and an improved electronic shift and throttle system; 
         FIG. 2  is a side view of an engine of one of the propulsion units of  FIG. 1 ; 
         FIG. 3  is a top view of the a control head of the marine vessel of  FIG. 1 ; 
         FIG. 4  is a schematic diagram illustrating the electronic shift and throttle system of  FIG. 1 ; 
         FIG. 5  is an elevation view of the control head of  FIG. 3  illustrating an operational range of a control lever thereof; 
         FIG. 6  is a table illustrating the lighting of indicator or gear lamps as the control lever of  FIG. 5  is moved through the operational range; 
         FIG. 7  is side elevation view of a shift actuator of the propulsion unit of  FIG. 2  illustrating an operational range of an actuator arm thereof; 
         FIG. 8  is a side elevation view of a throttle actuator of the propulsion unit of  FIG. 2  illustrating an operational range of an actuator arm thereof; 
         FIG. 9  is a side elevation view of the throttle actuator of  FIG. 8  illustrating a second side thereof; 
         FIG. 10  is a perspective view of the throttle actuator of  FIG. 8  illustrating the first side thereof; 
         FIG. 11  is a perspective view of the throttle actuator of  FIG. 8  illustrating the second side thereof; 
         FIG. 12  is a sectional view taken along line A-A of  FIG. 11 ; 
         FIG. 13  is a fragmentary side view, partially in section and partly schematic, of the throttle actuator of  FIG. 8 , a throttle, and a linkage therebetween; 
         FIG. 14  is a sectional view of the throttle of  FIG. 13  illustrating the throttle in an idle position; 
         FIG. 15  is a sectional view of throttle of  FIG. 13  illustrating the throttle in a wide open throttle (WOT) position; 
         FIG. 16  is a sectional view of throttle of  FIG. 13  illustrating movement of the throttle as the throttle controls are being calibrating; 
         FIG. 17  is a flow chart illustrating the logic of a throttle calibration method disclosed herein; 
         FIG. 18  is a schematic diagram illustrating the delay of shift and throttle functions; 
         FIG. 19  is set of tables illustrating the delay of shift and throttle functions; 
         FIG. 20  is perspective view of a joystick of the marine vessel of  FIG. 1 ; and 
         FIG. 21  is a simplified top plan view of the joystick of  FIG. 20  showing a guided plate inside the joystick and the axes of movement of the joystick; and 
         FIG. 22  is an elevation view of the joystick of  FIG. 20  illustrating an operational range of the joystick. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings and first to  FIG. 1 , this shows a marine vessel  10  which is provided with a plurality of propulsion units in the form of three outboard engines  12   a ,  12   b  and  12   c . However, in other examples, the marine vessel  10  may be provided with any suitable number of inboard and/or outboard engines. It is common to see two engines and practically up to five engines in pleasure marine vessels. The marine vessel  10  is also provided with a control head station  14  that supports a joystick  15  and a control head  16 . The joystick  15  and the control head  16  are each provided with a microprocessor (not shown). 
     A first one of the engines, namely the port engine  12   a , is best shown in  FIG. 2 . The port side engine  12   a  includes a shift actuator  18   a , a throttle actuator  20   a,  and an electronic servo module (ESM)  22   a;  all of which are disposed within a cowling  24 . Second and third ones of the engines, namely the center engine  12   b  and starboard  12   c  engine, have substantially the same structure as the port engine  12   a  and are accordingly not described in detail herein. 
     The control head  16  is best shown in  FIG. 3 . The control head  16  includes a housing  26 . A port control lever  30  and starboard control lever  40  are each pivotally mounted on the housing  26 . The port control lever  30  normally controls the shift and throttle functions of the port engine  12   a  but, in this example, also controls the shift and throttle functions of the center engine  12   b  both of which are shown in  FIG. 1 . The starboard control lever  40  controls the shift and throttle functions of the starboard engine  12   c  which is also shown in  FIG. 1 . In a marine vessel with five engines, the port control lever would control the shift and throttle functions of the port, center port and center engines while the starboard control lever would control the shift and throttle functions of the starboard engine and starboard center engine. Alternatively, the joystick  15  which is best shown in  FIG. 20  may be used to control the shift and throttle functions of the engines. 
     Referring back to  FIG. 3 , the port control lever  30  is provided with a master trim switch  50  which allows an operator to simultaneously trim all of the engines. The port and starboard engines are trimmed individually using a respective port trim button  31  and starboard trim button  41 , which are both disposed on the housing  26 . The center engine  12   b  is under the control of a center trim button  31  (not shown). 
     The housing  26  also supports a plurality of indicator or gear lamps which, in this example, are LED lamps. A port forward indicator  32 , port neutral indicator  34 , and port reverse indicator  36  are disposed on a side of housing  26  adjacent the port control lever  30 . A starboard forward indicator  42 , starboard neutral indicator  44 , and a starboard reverse indicator  46  are disposed on a side of housing  26  adjacent the starboard control lever  40 . A port neutral input means  38  and starboard neutral input means  48  are also disposed on the housing  26 . An RPM input means  52 , synchronization (SYNC) input means  54 , and SYNC indicator lamp  56  are also all disposed on the housing  26 . In this example, the port neutral input means  38 , starboard neutral input means  48 , RPM input means  52 , and SYNC input means  54  are buttons but any suitable input devices may be used. 
     As best shown in  FIG. 4 , the joystick  15  and the control head  16  together with the engines  12   a ,  12   b  and  12   c , and their corresponding shift actuators  18   a ,  18   b  and  18   c;  throttle actuators  20   a ,  20   b  and  20   c;  and ESMs  22   a ,  22   b  and  22   c , form part of an electronic shift and throttle system  60 . The electronic shift and throttle system  60  further includes a gateway  62  and a plurality of engine management modules (EMMs)  64   a ,  64   b  and  64   c . Each EMM is associated with a corresponding ESM. The control head, gateway, ESMs, and EMMs communicate with each other over a private CAN network  66 . The electronic shift and throttle system  60  is designed to support both the joystick  15  and the control head  16  as well as up to five engines. Components of optional fourth and fifth engines  12   d  and  12   e  are shown in ghost. 
     A single master ignition switch  68  provides power to the entire private CAN network  66 . However, start and stop functions are achieved by individual switches  70  read by the joystick  15  or the control head  16  as discrete inputs or serial data. Any command an operator inputs to the joystick  15  or the control head  16  to start, stop, trim, shift or accelerate one of the engines  12   a ,  12   b  or  12   c  is sent to the corresponding ESM  22   a ,  22   b  or  22   c  and corresponding EMM  64   a ,  64   b  or  64   c  over the CAN network  66 . The ESMs and EMMs are each provided with a microprocessor (not shown). In this example, a private network cable  72  that carries the CAN lines from the joystick  15  and the control head  16  to the engines  12   a ,  12   b  and  12   c  has two separate wires used to shut down the engines in the event that the CAN network  66  fails. 
     Information from the electronic shift and throttle system  60  is made available to devices on a NMEA2K public network  74  through the gateway  62 . The gateway  62  isolates the electronic shift and throttle system  60  from public messages, but transfers engine data to displays and gauges (not shown) on the public network  74 . The gateway  62  is also provided with a plurality of analog inputs  76  which may be used to read and broadcast fuel senders or oil senders or other resistive type senders such as rudder senders or trim tab senders on the public network  74 . 
     Referring now to  FIG. 5 , the port side  30  control lever is moveable between a forward wide open throttle (forward WOT) position and a reverse wide open throttle (reverse WOT) position, through a neutral position. An operator is able to control the shift and throttle functions of the port engine  12   a  by moving the port control lever  30  through its operational range. The port control lever  30  is also provided with a forward detent, neutral detent, and reverse detent all disposed between the forward WOT position and reverse WOT position. This allows the operator to physically detect when the port control lever  30  has moved into a new shift/throttle position. As shown in  FIG. 6 , the port forward indicator  32 , port neutral indicator  34 , and port reverse indicator  36  light up to reflect the position of the port control lever  30  shown in  FIG. 5 . 
     Referring back to  FIGS. 4 and 5 , the microprocessor supported by the control head  16  reads the position of the port control lever  30  and sends shift and throttle commands to the ESM  22   a  via the private CAN network  66 . The ESM  22   a  commands the shift actuator  18   a  and throttle actuator  20   a  which are best shown in  FIGS. 7 and 8 , respectively.  FIG. 7  shows that the shift actuator  18   a  has an actuator arm  19   a  which is moveable between a forward position and a reverse position with a neutral position therebetween.  FIG. 8  shows that the throttle actuator  20   a  has an actuator arm  21   a  which is moveable between an idle position and a wide open throttle (WOT) position. An actuator position sensor  142 , shown in  FIG. 12 , signals the actuator position to the ESM  22   a  shown in  FIG. 4 . This feedback may be used to govern the control head  16 . The shift and throttle functions of the port side engine  12   a  are thereby controlled. It will be understood by a person skilled in the art that the shift and throttle functions of the starboard engine  12   c  are controlled in a similar manner using the starboard control lever  40  shown in  FIG. 2 . The shift and throttle functions of the center engine  12   b  are under the control of the port control lever  30  in this example. 
     Likewise, and with reference to  FIGS. 21 and 22 , the joystick  15  is moveable between a forward wide open throttle (forward WOT) position and a reverse wide open throttle (reverse WOT) position, through a neutral position along its Y-axis of movement. An operator is able to control the shift and throttle functions of the engines by moving the joystick  15  through its operational range. The joystick  15  is also provided with a forward detent, neutral detent, and reverse detent all disposed between the forward WOT position and reverse WOT position. This allows the operator to physically detect when the port joystick  15  has moved into a new shift/throttle position. The microprocessor supported by the joystick  15  reads the position of the joystick and sends shift and throttle commands to the ESM  22   a  via the private CAN network  66 . Accordingly, either the joystick  15  or control head  16  may be used to control shift and throttle functions. However, as shown in  FIG. 21 , the joystick  15  is also moveable along an X-axis, Y-axis, and θ-axis to allow for vector thrusting. A guided field plate  60  provides preferential joystick movement. 
     The electronic shift and throttle control system  60  disclosed herein is also provided with an improved shift actuator  18   a  and throttle actuator  20   a  as shown in Figures actuators as shown in  FIGS. 7 and 8  respectively. The shift and throttle actuators are both rotary actuators which have substantially the same structure and function in substantially the same manner, with the exception of the actuator arm  19   a  or  21   a . This will be understood by person skilled in the art. Accordingly, only the throttle actuator  20   a  is described in detail herein. 
     Referring to  FIGS. 7 through 11 , the throttle actuator  20   a  of the port engine  12   a  is shown in greater detail. The throttle actuator  20   a  generally includes a waterproof housing  112  which encases various components, a motor  114  extending from and bolted to the housing  112 , and a harness  116  for electrically connecting the throttle actuator  20   a  to the electronic shift and throttle system  60 . The housing  112  is provided with a plurality of mounting holes  118   a ,  118   b ,  118   c , and  118   d  allowing the throttle actuator  112  to be mounted as needed. In this example, the housing  112  also includes a body  120  and a cover  121  bolted the body  120 . Removing the cover  121  provides access to the various components encased in the housing  112 . The motor  114  may be rotated in either a first rotational direction or a second rotational direction opposite to the first direction depending on the direction of the electric current supplied to the motor  114 . As best shown in  FIG. 11 , the harness  16  is wired to the motor  114  and supplies an electric current thereto. 
     Referring now to  FIG. 12 , the housing  112  encases a worm gear  122  which is coupled to an output shaft (not shown) of the motor  114 . The worm gear  122  engages a worm wheel  124  which is integrated with a spur gear pinion  126 . The worm gear  122  imparts rotary motion to both the worm wheel  124  and spur gear pinion  126 . The spur gear pinion  126  imparts rotary motion to a sector spur gear  128  which is integrated with an output shaft  130  of the throttle actuator  20   a . The output shaft  130  is thereby rotated by the motor  114 . Bearings  132   a  and  132   b  are provided between the output shaft  130  and the housing  112  to allow free rotation of the output shaft  130  within the housing  112 . A sealing member in the form of an O-ring  134  is provided about the output shaft  130  to seal the housing. 
     As best shown in  FIG. 11 , the distal end  136  of the output shaft  130  is splined. There is a longitudinal, female threaded aperture  138  extending into the output shaft  130  from the distal end  136  thereof. The aperture  138  is designed to receive a bolt to couple the output shaft  130  to the actuator arm  21   a  as shown in  FIG. 8 . Referring back to  FIG. 12 , there is a magnet  140  disposed at a proximal end  141  of the output shaft  130 . There is also a position sensor  142  which senses a position of the magnet  140  as the output shaft  130  rotates. The position sensor  142  is thereby able to determine the rotating position of the output shaft  142 . In this example, the position sensor  142  is a Hall Effect sensor but in other embodiments the sensor may be a magnetoresistive position sensor or another suitable magnetic rotational sensor. The position sensor  142  is mounted on a circuit board  144  which is mounted on the throttle actuator housing  112 . More specifically, in this example, the circuit board  144  is mounted on the housing cover  121 . As best shown in  FIGS. 9 and 10 , the circuit board  144  is wired to the harness  116  allowing the position sensor  142  to send an electrical signal to the ESM  22   a  which is shown in  FIG. 4 . 
     As best shown in  FIG. 13 , the actuator arm  21   a  is coupled to a throttle  150  of the port engine  12   a , shown in  FIG. 2 , by a throttle linkage  152 . The throttle  150  includes a throttle body  154  and a throttle plate  156  mounted on a rotatable throttle shaft  158 . There is also a throttle position sensor (TPS)  159  mounted on top of the throttle shaft  158  which senses the position of the throttle shaft as it rotates. In this example, the TPS  159  is a potentiometer and communicates with the EMM  64   a  shown in  FIG. 4 . Together the plate  156 , the shaft  158  and the TPS  159  form a butterfly valve member which is spring loaded to a closed position shown in  FIG. 14 . Referring back to  FIG. 13 , rotation of the actuator output shaft  130  drives the actuator arm  21   a  to rotate the throttle shaft  158 . Rotation of the throttle shaft  158  causes the throttle  150  to move between an idle position shown in  FIG. 14  and a WOT position shown in  FIG. 15 . Whether the throttle  150  is in the idle position or WOT position is dependent on the rotational position of output shaft  130 . The throttle actuator  20   a  is an external actuator, the electronic shift and throttle system  60  may be installed as a kit on an existing engine. 
     To correlate position of the throttle  150  with the position of the actuator arm  21   a , it is necessary calibrate the throttle controls of the electronic shift and throttle system  60 . Once calibrated, the idle position of the actuator arm  21   a  will correspond to the idle position of the throttle  150 . 
     The ESM  22   a , shown in  FIG. 4 , calibrates the throttle controls by using the voltage level sent by the TPS  159 , the duty cycle of the electrical signal sent by the actuator position sensor  142  and the amount of current flowing into the actuator motor  114 . The voltage level of TPS  159  varies with the position of the throttle plate  156 . In this example, the voltage level of TPS  159  is low when the throttle plate  156  is perpendicular and in contact with throttle housing  154 , as shown in  FIG. 14 , and the voltage level of the TPS  159  is high when the throttle plate  156  is parallel with throttle housing  154  as shown in  FIG. 15 . The duty cycle of the electrical signal sent by the actuator position sensor  142  varies with the position of the throttle actuator arm  21   a . In this example and as shown in  FIG. 13 , the duty cycle of position sensor  142  is low when the actuator arm  21   a  at the idle position and is high when the actuator arm  21   a  is at the WOT position. The amount of current flowing into the actuator motor  114  is low when the actuator arm  21   a  moves freely and increases when the throttle plate  156  is in contact with the throttle housing  154  thereby stalling the motor  114 . 
     The ESM  22   a  calibrates the throttle controls by determining the throttle position where the TPS voltage is the lowest, while avoiding residual tension in the throttle linkage  152 . This is done by  20  opening the throttle  150  and moving it back to the idle position in increments. This is best shown in ghost in  FIG. 16 . The ESM  22   a  controls the opening of the throttle  150  and moves the throttle  150  back to the idle position. In this example, the throttle  150  is moved back in increments of 1° towards a hard stop, i.e. where the throttle plate  156  comes into contact with the throttle housing  154 . At each increment the ESM  22   a  communicates  25  with the EMM  64   a  and requests the voltage level of the TPS  159  shown in  FIG. 13 . The ESM  22   a  stores the value. This is repeated until the throttle plate  156  comes to the hard stop. The ESM  22   a  determines if the throttle  150  is at the hard stop by measuring the current flowing in the actuator motor  114 . The ESM  22   a  assumes that the throttle  150  is at the hard stop if the current is above a pre-determined value. The ESM  22   a  then establishes the idle position as being where the lowest valid voltage level that is at least a minimal distance away from hard stop was measured. The minimal distance from the hard stop ensures that the tension created in the throttle linkage  152  while moving the throttle plate  156  against the hard stop is released. In this example, the minimal distance is defined in degrees and set to 0.75°. However, the minimal distance may range for example between 0.3° and 1.5°. 
     In this example, the calibration procedure will terminate successfully if the following parameters are met:
     1. The voltage level of the signal from the throttle position sensor has changed more than the movement amount while calibrating (in this example 0.2V). This amount confirms the actuator actually moved the throttle plate.   2. The minimum expected idle position voltage level (in this example 0.3V)&lt;=the voltage level of the signal from the throttle position sensor in the idle position&lt;=the maximum expected idle position voltage level (in this example 0.62V).
 
The values may vary in other embodiments.
   

       FIG. 17  best shows the above described calibration procedure. The new calibration position is stored in EEPROM if the calibration procedure terminates successfully. A similar calibration procedure is used for the center and starboard engines. 
     Referring back to  FIG. 3 , once the calibration procedure is completed, the operator can more accurately increase or decrease engine throttle by moving the joystick  15  or the port control lever  30  through its operational range. The operator can also shift gears by moving the joystick  15  or the port control lever  30  through its operational range. The control head  16  sends shift and throttle commands to the ESM  64   a  which is shown in  FIG. 4 . The ESM  64   a  then commands the shift actuator  18   a  and the throttle  20   a  actuator of the port engine  12   a . However, the ESM  64   a  will not command the shift actuator  20   a  to shift gears if the engine speed is above a predetermined maximum threshold speed, even if the ESM  64   a  is commanded to do so by the control head  16 . In this example, the predetermined maximum threshold speed is 1,500 RPM. Instead the ESM  64   a  will command the throttle actuator  18   a  to move to the idle position in order to lower the engine speed. The ESM  64   a  will also command the throttle actuator  18   a  to move to the idle position when an actual gear of the port engine  12   a  is not the same as a commanded gear. 
       FIG. 18  shows a method for delaying shift commands  212  and throttle commands  214  for the port engine  12   a . When the control head  16  is used input shift and throttle functions a position sensor  33 , that is part of the control head  16 , reads the position of the port control lever  30 . When the joystick  15  is used input shift and throttle functions a position sensor  35 , that is part of the joystick  15 , reads the position of the port joystick  15 . The joystick  15  or control head  16  then sends shift and throttle commands  212  and  214  to the ESM  64   a  of the port engine  12   a  over the CAN network  66 . The shift and throttle commands  212  and  214  are based on the position of the joystick  15  or the port control lever  30 . The ESM  64   a  commands the shift actuator  18   a  and throttle actuators  20   a  of the port engine  12   a . The port engine  12   a  is also provided with a speed sensor  13   a . The speed sensor  13   a  signals the engine speed to the EMM  22   a . The EMM  22   a  communicates the engine speed  216  to the ESM  64   a  over the CAN network  66 . The ESM  64   a  will delay commanding the shift actuator  18   a  to shift gears if the engine speed is above the predetermined maximum threshold speed of 1,500 RPM. Meanwhile, the ESM  64   a  will command the throttle actuator  18   a  to move to the idle position. This eventually causes the engine speed to drop below 1,500 RPM. The ESM  64   a  then commands the shift and throttle actuators  18   a  and  20   a  in accordance with the shift and throttle commands  212  and  214  received from the joystick  15  or the control head  16 . To prevent stalling, the ESM  64   a  will not command the shift actuator  20   a  to shift gears unless the engine speed  216  is above a predetermined minimum threshold speed. In this example, the predetermined minimum threshold speed is 800 RPM. However, in other examples, the minimum threshold value may be in the range of 500 RPM to 1100 RPM. 
       FIG. 19  is a graphical representation which shows delaying shift and throttle commands based on engine speed. The following is a description of the steps illustrated.
     STEP  0 —The joystick or the control lever is in a forward position, the engine is in forward gear, and the engine speed is above the predetermined maximum threshold speed.   STEP  1 —The operator quickly moves the joystick or the control lever from the forward position to a reverse position. The ESM commands the throttle actuator to move the throttle to the idle position   STEP  2 —The throttle is kept at the idle position to allow the engine speed to drop.   STEP  3 —The ESM waits until the engine speed drops below the predetermined maximum threshold speed before commanding the shift actuator to shift to neutral.   STEP  4 —The ESM commands the shift actuator to shift into neutral after the engine speed drops below the predetermined maximum threshold speed (T 1 ).   STEP  5 —The ESM applies the throttle command after the shift actuator shifts into neutral. This causes the engine speed to increase.   STEP  6 —The ESM applies the shift command after the engine speed rises above the predetermined minimum threshold speed (T 2 ). This prevents the engine from stalling.   STEP  7 —The ESM commands the shift actuator to shift into reverse.   

     Accordingly, and with reference to  FIG. 4 , if the operator quickly moves the joystick  15  or the control lever  30  from the forward WOT position to the reverse WOT position, the ESM  64   a  will not command the shift actuator  18   a  to shift gears until the engine speed drops below 1,500 RPM. The same logic applies when the joystick or the control lever is moved from a reverse position to a forward position. 
     The method and system for delaying shift and throttle commands based on engine speed disclosed herein allows an operator to quickly shift from forward high throttle to reverse high throttle or vice versa without overstressing the gear box and while helping to prevent the engine from stalling under the high opposite force of a propeller. 
     It will be understood by a person skilled in the art that the method and system for delaying shift and throttle commands based on engine speed disclosed herein may be implemented in any electronic shift and throttle control system, regardless of whether the vehicle is a marine vessel. 
     It will further be understood by a person skilled in the art that many of the details provided above are by way of example only, and are not intended to limit the scope of the invention which is to be determined with reference to following claims.
A method for delaying shift and throttle commands based on engine speed comprises establishing a predetermined threshold engine speed. Shift and throttle commands are calculated based on the position of a joystick which allows an operator to manually control shift and throttle functions. Execution of the shift and throttle commands is delayed if the engine speed is above the predetermined maximum threshold engine speed.