Abstract: Non-linear control laws are disclosed and implemented with a controller and control system for maneuvering an underwater vehicle. The control laws change the phase of one Inferior-Olive (IO) neuron with respect to another IO. One control law is global, that is, the control law works (stable and convergent) for any initial condition. The remaining three control laws are local. The control laws are obtained by applying feedback linearization, while retaining non-linear characteristics. Each control law generates a profile (time history) of the control signal to produce a desired phase difference recognizable by a controller to respond to disturbances and to maneuver an underwater vehicle.

Abstract: A hybrid propulsion and energy management system for use in marine vessels and other variable demand propulsion applications monitors and draws energy from various energy sources dynamically to implement multiple operating modes and provide efficient system operation across a range of propulsive demands, altering the operation and output of various energy sources in response to propulsive load demands, hotel loads and auxiliary energy demands. The propulsion system incorporates at least two propulsive sources, including at least one main propulsive engine and at least one motor-generator unit arranged to drive a common output shaft, and the energy management system dynamically shifts operation of each of the two sources to satisfy propulsive demands. The main propulsive engine and the motor-generator unit are capable of driving the common output shaft both independently and simultaneously.

Abstract: An outboard motor includes an outboard motor main body, an attachment mechanism, a pivoting mechanism, an angle detecting device, a rotation speed detecting device, and a controller. The pivoting mechanism includes a first cylinder arranged to support and pivot the outboard motor main body about a horizontal shaft from a first angle to a second angle greater than the first angle. An angle detection value and a speed detection value are input into the controller. The controller is arranged to execute a speed reduction control to control the engine so as to reduce the engine speed. The controller is arranged not to execute the speed reduction control when the angle detection value is a value corresponding to the inclination angle less than the first angle or a value corresponding to the inclination angle greater than the second angle.

Abstract: There is provided a boat (200) including a hull (20), and two engines (30, 50) couplable to rotationally drive mutually spaced separate corresponding propeller assemblies for providing thrusts. Directions of the thrusts are angularly adjustable (?1, ?2) relative to the hull (20). A control unit (70) receives first and second user commands (S1, S2) and sends corresponding signals for controlling powers (P1, P2) coupled from the engines (30, 50) to their propeller assemblies. The control unit (70) determines a difference in power (?P) to be coupled to the propeller assemblies as a function of the first and second user commands (S1, S2). The control unit (70) controls coupling of power (P1, P2) to the propeller assemblies so that the propeller assemblies develop a difference in thrust which is a function of the difference in power (?P).

Abstract: A waterjet based propulsion system and method that utilizes more than one waterjet outlet port and controls the selective application of power to the waterjets with a splitter gearbox thereby improving the efficiency of the marine craft at low and high speeds.

Abstract: A mixed-mode method for operating a vehicle's propulsion plant to travel at a selected average speed using the minimum amount of fuel. The method involves travelling in one mode at high speed part of the time, and in a different mode at low speed part of the time, in such a way that the average speed is the selected value.

Abstract: A hybrid marine vessel is provided with a system that inhibits the movement of the marine vessel under its own power when the marine vessel is connected or recharging to a stationary source of energy on shore. This avoids significant damage that could otherwise occur if the marine vessel moves away or attempts to move away from the dock when connected by a cable or other device to a stationary structure. The system detects a potential connection between the boat and a stationary shore component, such as a source of energy, and inhibits the transmission from being placed in a forward or reverse gear position under those conditions. Similarly, if the boat is already in a forward or reverse gear position, the system inhibits its being placed into a battery recharging mode.

Abstract: An outboard motor includes a prime mover, a marine propulsion unit having a propeller arranged to be driven by a rotational force of the prime mover to generate a thrust force, a shift position changing mechanism, a shift position changing mechanism actuator, and a control unit arranged to control the shift position changing mechanism actuator. When the shift position is changed to one of the first shift position and the second shift position from the neutral position, the control unit inhibits a change in the shift position to the other one of the first shift position and the second shift position until a predetermined time period elapses. The above arrangement improves the controllability of a boat propulsion system having an electronically controlled shift mechanism.

Abstract: A speed control system for a small planing boat can comprise a speed sensor to detect a vessel speed of a boat body, a speed information storing unit on which data of a previously set maximum speed limit of the boat body is stored, and a speed control device for controlling the cruising speed of the boat body not to exceed the maximum speed limit based on a result of a correlation between the cruising speed and the maximum speed limit. The speed control device can comprise a revolution speed sensor, a revolution speed acquiring unit and a revolution speed control unit. The speed control device can also work in conjunction with an intake air mass amount control device which can include an electronically-controlled throttle valve, an air mass amount acquiring unit and a throttle opening degree control unit.

Abstract: A personal watercraft comprises a water jet pump configured to be driven by an engine to generate a rearward water jet, a reverse bucket mounted at a periphery of the water jet pump and movable between a forward driving position and a reverse driving position, a driving power operation member configured to control an engine driving power, a reverse driving operation member configured to change a position of the reverse bucket from the forward driving position to the reverse driving position, and a deceleration operation member, wherein the reverse bucket is in the forward driving position when the deceleration operation member and the reverse driving operation member are not operated, and the reverse bucket is in a deceleration position between the forward driving position and the reverse driving position when the deceleration operation member has been operated and the reverse driving operation member is not operated.

Abstract: A marine vessel includes a hull and a jet propulsion device arranged to take in water through an intake port and eject the water through an ejection port rearward with respect to the hull. The ejection port is arranged posterior to the intake port. The marine vessel also includes a reversing member arranged to be movable between a forward drive position and a reverse drive position. The reversing member is arranged to, when placed at the reverse drive position, reverse the direction of the water ejected from the jet propulsion device forward with respect to the hull (in a direction capable of generating a propulsive force in the reverse drive direction). The marine vessel further includes an operation unit arranged to be operated by a marine vessel maneuvering operator to locate the reversing member at the forward drive position or the reverse drive position, and an internal combustion engine arranged to drive the jet propulsion device.

Abstract: A marine propulsion system includes a power source, a propeller, a shift mechanism, a control lever, a rotational speed sensor, and a control device. The shift mechanism is switchable among three shift positions including forward, neutral, and reverse. The control lever is operable by the marine vessel operator to switch the shift position of the shift mechanism. The rotational speed sensor detects the rotational speed of the propeller. The control device controls at least one of the power source and the shift mechanism so as to reduce the rotational speed of the propeller if the rotational speed sensor detects a rotational speed of the propeller when the control lever is in a position corresponding to the neutral shift position. As a result, the propeller is prevented from rotating when a control lever is in a neutral position.

Abstract: In an apparatus for controlling operation of an outboard motor having an internal combustion engine, a transmission, and a trim angle regulation mechanism, where operation of the transmission is controlled to change the gear position from a second speed to a first speed when detected throttle change amount not less than a first predetermined value and operation of the trim angle regulation mechanism is controlled to start the trim-up operation such that the trim angle converges to a predetermined angle, the operation of the trim angle regulation mechanism is controlled such that the trim angle is decreased based on the detected rudder angle when steering of the outboard motor is started, thereby enabling to appropriately prevent cavitation caused by steering of the outboard motor, so that the boat can be smoothly turned.

Abstract: A boat includes a steering load detector arranged to calculate an output value of a steering motor necessary for steering an outboard motor in a traveling state, a motor output detector arranged to detect a possible output value that can be output by the steering motor, a prediction determination unit arranged to compare the necessary output value from the steering load detector with the possible output value from the motor output detector, and an electric power load control unit arranged to perform a control operation so as to increase a battery charge amount and/or to reduce the electric power load when the necessary output value is determined to be larger than the possible output value. As a result, the boat that can effectively perform steering when a motor output becomes small as a result of a reduced battery charge amount.

Abstract: In an apparatus for controlling a small boat having a hull and two outboard motors mounted on a stern of the hull and an actuator adapted to open/close a throttle valve of each engine of the motors for regulating speed of the engine, acceleration acting on the boat in a direction of gravity axis when the boat ascends or descends the ocean wave and angular acceleration about the gravity is detected and a correction amount of the engine speed is calculated based on the detected acceleration so as to change behavior of the boat, thereby mitigating a burden on the operator and improving stability of the boat.

Abstract: A method for controlling operation of a propulsion system of a waterborne vessel, comprising adjusting recovery of energy generated from the propulsion system to maintain position of the waterborne vessel in response to at least an indication of vessel position.

Abstract: A jet-propulsion personal watercraft comprises a body including a hull and a deck, an engine mounted in the body, a driving power output changing system configured to be able to change a driving power output of the engine, a controller configured to control an operation of the driving power output changing system, and a pressure sensor configured to be able to detect a pressure which is applied to the body from the water on which the body is floating, the pressure having a component in a lateral direction of the body, wherein the controller includes a turning determiner configured to determine whether or not the body is turning, based on a signal received from the pressure sensor; and a driving power output control unit configured to control the driving power output changing system based on information received from the turning determiner.

Abstract: A control device for propulsion units is adapted to synchronize the engine rotational speeds of a plurality of propulsion units arranged in a row on a vessel and operatively and electrically connected to two control levers that are positioned adjacent to each other. The control device synchronizes the engine rotational speeds by correcting the throttle opening of a target propulsion unit or units based on a deviation between the engine rotational speed of a reference propulsion unit and the engine rotational speed of the target propulsion unit. Upon cancellation of synchronization, the throttle opening correction is reduced stepwise from its corrected throttle opening to its natural throttle opening based on the position of the corresponding control lever. As such, large fluctuations in engine speeds are avoided upon cancellation of synchronization.

Abstract: A boat propulsion system includes a control section, a thrust calculation section, a thrust generating unit, a thrust detection section, and a control section. An operating amount is input to the control lever by operation of an operator. An accelerator detector detects the input operating amount of the control lever. The thrust calculation section calculates a thrust intended to be generated from the operating amount of the control lever to output a calculated thrust. The thrust generating unit generates a thrust. The thrust detection section detects a thrust actually generated on the thrust generating unit to output it as an actual thrust. The control section controls an output of the thrust generating unit so that the actual thrust approaches the calculated thrust.

Abstract: In an apparatus for preventing theft of plural, such as two, outboard motors (12F, 12S) adapted to be mounted on a boat, each of the outboard motors having an engine (16F, 16S), an engine controller (24F, 24S), and an authenticator (26F, 26S) that acquires ID information (A, B) from an electronic key (30F, 30S) when the key is brought close thereto by an operator, and gives permission to the engine controller to start the engine when the acquired ID information corresponds with the authentication ID information, and communicates with the engine controller of other outboard motor to notify that the permission to start the engine was given, thereby enabling the operator to easily start the outboard motors installed on one boat and having their respective authenticators.

Abstract: A boat propulsion system includes a shift mechanism arranged to change a shift position among forward, neutral, and reverse. A shift position detection mechanism is connected to a control lever with a wire. The shift position detection mechanism has a detected member and a position detection section. The detected member is displaced corresponding to an operation position of the control lever as the control lever is operated. The position detection section detects a position of the detected member. The position detection section outputs a shift position signal corresponding to the detected position of the detected member. A control device controls the shift position of the shift mechanism on the basis of the shift position signal. The boat propulsion system provided with the shift mechanism of an electronic control type can replace a boat propulsion system provided with a shift mechanism of a mechanical type at low cost.

Abstract: There is provided a watercraft in which a controlling state before a start-up changes less easily and an operating state of a remote controller and a remote controller lever for operating the watercraft propulsion unit is easily kept stable, although at least one of watercraft propulsion units has been in operation and other watercraft propulsion unit(s) starts-up. Remote controllers are connected to watercraft propulsion units. The remote controllers include controlling units, and remote controller levers corresponding to the watercraft propulsion units. The controlling units are mutually connected together to communicate with each other. When one of the watercraft propulsion units has been in operation and the other one start-up from a stop state, the controlling unit corresponding to the start-up watercraft propulsion unit recognizes a controlling state of the controlling unit in operation and controls to agree with the controlling state thereof.

Abstract: A watercraft propulsion system has a control lever for giving instructions regarding the operating mode as well as the amount of output power from a source of driving force, and a controller for setting a propeller driving mode according to the instruction given by the control lever. When a reverse mode is instructed by the control lever, the controller sets the propeller driving mode depending on certain considerations such as user settings and battery charge. For instance, the controller may set the propeller driving mode to a mode in which the propeller is rotated in reverse by an electric motor or by the engine. Also, the controller may regulate electric power supply to the motor in light of battery charge. Other combinations are also contemplated.

Abstract: A steering wheel, operable by an operator, can be electrically connected to an electric motor to provide an actuation signal corresponding to the amount of a steering wheel operation to the electric motor, a reaction motor for applying a reaction to the steering wheel, and an ECU for controlling the electric motor are provided. The ECU can include at least one of an operation status detection device for detecting an operation status corresponding to the steering wheel operation, a running status detection device for detecting a running status of the watercraft, an outboard motor status recognition device for recognizing a status of the outboard motor, such as the installation number thereof, and an electric motor status detection device for detecting a status of the electric motor.

Abstract: A boat propulsion system includes a gear shift mechanism arranged to transmit a driving force generated by an engine to first and second propellers at one of at least a low speed reduction ratio and a high speed reduction ratio, and a control section arranged to perform control so as to shift a speed reduction ratio of the gear shift mechanism based on first and second gear shift control maps when an acceleration command from a user is detected. The first and second gear shift control maps define a region to shift the speed reduction ratio of the gear shift mechanism using two parameters, preferably a rotational speed of the engine and a lever opening degree of a lever of a control lever portion. The boat propulsion system achieves both the acceleration performance and the maximum speed desired by a user.

Abstract: A method for controlling operation of a propulsion system of a waterborne vessel, comprising adjusting recovery of energy generated from the propulsion system to maintain position of the waterborne vessel in response to at least an indication of vessel position.

Abstract: A motorized surfboard comprises top and bottom shells. The top shell comprises recesses that may contain motors, batteries, and motor controllers. The bottom shell comprises recesses that may contain one or more impellers. The impellers may be connected to the motors by shafts that extend through passageways between recesses in the top and bottom shells. The motors may be controlled by the user with various hand, arm, or leg motions. This may be accomplished by providing an accelerometer on the user. Orientation and motion sensed by the accelerometer may be translated to motor commands and these commands may be transmitted wirelessly to the motor controllers.

Abstract: A marine outboard engine has upper and lower engine covers, a swivel bracket, a stern bracket, an engine, a driveshaft, a gear case, a propeller shaft, and a variable pitch propeller. A hydraulic system includes hydraulic steering, trim, and propeller pitch actuators, and at least one valve having at least one inlet, and first, second, and third outlets. The first, second, and third outlets fluidly communicate with the hydraulic steering, trim, and propeller pitch actuators respectively. A pump fluidly communicates with the at least one inlet of the at least one valve. A reservoir stores hydraulic fluid. A control unit controls the at least one valve to control a flow of hydraulic fluid through each of the first, second, and third outlets based at least in part on a signal received from a pressure sensor. Methods of controlling the hydraulic systems are also disclosed.

Abstract: A boat propulsion system includes a power source, a propulsion unit, a propeller rotational speed detection section, a shift mechanism, an actuator, a control lever, a shift position detection section, an accelerator opening detection section, and a control unit. When the control lever is operated such that a shift position is changed from a first shift position to a second shift position, while the absolute value of accelerator opening varying speed becomes equal to or larger than a predetermined value, the control unit enables the actuator to maintain the first shift position until the rotational speed of a propeller becomes equal to or lower than a predetermined rotational speed and then to change to the second shift position. This minimizes a load generated on the power source, the power transmission mechanism, and other components of the boat propulsion system.

Abstract: A method is provided for controlling a drive arrangement in a watercraft. The method includes detecting thrust and steering commands from an operating device which is connected to a control unit, and controlling the drive arrangement based on detected commands from the operating device for obtaining a desired course of travel of the watercraft, wherein a force is generated which acts towards a defined position on the watercraft. The method furthermore includes determining the speed of the watercraft and adapting the position on which the force from the drive arrangement acts as a function of at least the speed and as a function of the influence of the position of the center of pressure of the watercraft, thereby maintaining the desired course of travel. An arrangement for controlling a drive arrangement in a watercraft is also provided.

Abstract: A control device for a marine engine comprised so that a section of an angle sufficiently narrower than a crank angle corresponding to each stroke of a combustion cycle of the engine is set as an instantaneous speed detection section, a crank angle position that appears every time the engine rotates in the instantaneous speed detection section is detected as a specific crank angle position, an instantaneous rotational speed of the engine is detected every time each specific crank angle position is detected, it is determined whether the engine needs to be assisted from the degree of reduction in the instantaneous rotational speed, and a motor-generator including a rotor directly connected to a crankshaft of the engine is driven to apply a drive force from the motor-generator to the engine when it is determined that the engine needs to be assisted.

Abstract: An automatic speed control system that provides desired watercraft velocity over land. The coupled algorithms correct engine speed and torque using inertia based measurements, GPS, and tachometer measurements, and the corrections are augmented and enhanced by velocity/speed and torque/speed relationships that are dynamically and adaptively programmed with real-time data collected during replicated operations of the watercraft in specified conditions.

Abstract: A control handle for a vessel, the control handle having a handle bar, two handles, at least one throttle control arranged in connection with one or both handles, and an additional control. A vessel having a control handle for a vessel with a handle bar, two handles, at least one throttle control arranged in connection with one or both handles, and an additional control. The throttle control can be a twist grip. The additional control can be for adjustment of one or several of: shifting between forward or backward propulsion of the vessel, force distribution between motors provided on the vessel, adjustment of an angular position of trimming tabs of the vessel, adjustment of a banking angle of a propeller drive provided in the vessel, and adjustment of a position of a reversing scoop of a water jet.

Abstract: In recreational boats, multiple drive units, e.g., multiple outboard motors, Z-drives, or jet drives, are often provided to propel the boat, at least one of the drive units having a propulsion reversal function for executing a reverse propulsion. To facilitate execution of a turning maneuver with a boat in an extremely tight space, and to ensure that even an unskilled person is able to reliably execute such a turning maneuver, it is provided that the drive units be activated automatically for executing the turn on the spot as a function of a command for turning. The command may be made via a switch, which is operated by the driver of the boat. One drive unit is then operated automatically in propulsion reversal mode, and the other drive unit is operated in propulsion mode. The power of the drive units is then controlled in such a way that the instantaneous efficiency of the drive units operated during turning is taken into account.

Abstract: An aeration control system and method for a marine vessel. The system includes a valve configured to be coupled to an aeration conduit of a marine vessel. The valve is configured to be responsive to a valve control signal having a first value so as to be open and to provide air to the aeration conduit, and the valve configured to be responsive to the valve control signal having a second value so as to be closed and not provide air to the aeration conduit.

Abstract: A marine engine control system comprising a water jacket, an outlet sensor, and a control module. The water jacket directs a flow of water across a catalytic converter to cool the catalytic converter. The outlet sensor module measures an actual temperature of the water. The control module determines an expected temperature of the water when the catalytic converter is functional.

Abstract: A shift system for a boat propulsion unit is provided comprising a remote control operation device having a remote control shift lever for shifting from a distance. A boat propulsion unit has a shift device for shifting and a shift actuator for actuating the shift device. A controller controls the actuation of the shift actuator according to the operation amount of the remote control shift lever, as the remote control shift lever is operated from a neutral position within a specified range of shift region. The controller controls the actuation amount of the shift actuator per unit operation amount of the remote control shift lever to be different in part of the shift region.

Abstract: Methods and systems are provided for controlling a propulsion system of a vessel including an engine and a propeller. In one embodiment, the method comprises independently adjusting each of an engine setting and a propeller setting responsive to real-time vessel operating data.

Abstract: In an apparatus for controlling operation of an outboard motor mounted on a boat and having a torque converter equipped with a lockup clutch, it is configured to have a clutch controller that controls the lockup clutch to ON when a speed ratio of the torque converter is equal to or greater than a reference value, the clutch controller being configured to determine whether a throttle valve is at about a fully-opened position and to control the lockup clutch to ON when the speed ratio becomes equal to or greater than a predetermined value set smaller than the reference value before the speed ratio reaches the reference value, and the throttle valve is discriminated to be at about the fully-opened position. With this, it becomes possible to reliably make a lockup clutch ON when the acceleration is completed, so that the boat speed can reach the maximum speed.

Abstract: In an apparatus for controlling operation of an outboard motor mounted on a boat and having a torque converter equipped with a lockup clutch, it is configured to calculate a speed ratio of the torque converter based on an input rotation speed and output rotation speed of the torque converter, detect manifold absolute pressure of the engine, control the lockup clutch to ON when the calculated speed ratio has been equal to or greater than a reference value, and control the lockup clutch to OFF when the manifold absolute pressure has been decreased by a first predetermined value or more. With this, it becomes possible to prevent the boat speed from decreasing even when the resistance of water flow acting on the boat increases due to the influence of a wave etc., thereby maintaining the maximum speed.

Abstract: A marine vessel control apparatus is arranged to start and stop engines that are respectively provided in multiple propulsion devices. The marine vessel control apparatus includes multiple individual start/stop switches arranged to correspond to the respective multiple propulsion devices and arranged to be operated by an operator to individually start and stop the engines in the respective multiple propulsion devices, an all-device start/stop switch arranged to be operated by the operator to collectively start and stop the engines in the multiple propulsion devices, an operating state acquiring unit arranged to acquire operating states of the engines in the respective multiple propulsion devices, and a control unit. The control unit includes multiple input ports corresponding to the respective multiple individual start/stop switches. Each of the input ports is connected with the corresponding individual start/stop switch. All of the input ports are connected commonly with the all-device start/stop switch.

Abstract: A marine vessel propulsion system includes a plurality of propulsion devices, each including a motor and a propeller rotated by the motor.

Abstract: A personal watercraft can have a steering nozzle pivoting in accordance with the operation of a steering handle unit to change the traveling direction of a vehicle body. A steering position sensor can be configured to detect the steering angle of the steering handle unit. An actuator can be arranged to pivot the steering nozzle to change the steered angle thereof. A running speed sensor can be configured to detect the running speed of the vehicle body, and a control device. The control device can determine an operational amount of the actuator and control the actuator based upon the detection amount of the steering position sensor, the running speed sensor, and a steering ratio preset with reference to the steering angle and the running speed. The steering ratio is set to be smaller as the running speed becomes larger.

Abstract: A speed control system for a small planing boat can comprise a speed sensor to detect a vessel speed of a boat body, a speed information storing unit on which data of a previously set maximum speed limit of the boat body is stored, and a speed control device for controlling the cruising speed of the boat body not to exceed the maximum speed limit based on a result of a correlation between the cruising speed and the maximum speed limit. The speed control device can comprise a revolution speed sensor, a revolution speed acquiring unit and a revolution speed control unit. The speed control device can also work in conjunction with an intake air mass amount control device which can include an electronically-controlled throttle valve, an air mass amount acquiring unit and a throttle opening degree control unit.

Abstract: A water jet propulsion boat includes a fuel pump driven by an electric control unit and arranged to deliver fuel from a fuel tank to an engine via a fuel pipe, and a fuel pressure sensor arranged to detect a pressure of the fuel delivered to the engine by the fuel pump. When a magnitude of the fuel pressure detected by the fuel pressure sensor is less than a predetermined magnitude, the fuel pump is activated. On the other hand, when the magnitude of the fuel pressure detected by the fuel pressure sensor is equal to or greater than the predetermined magnitude, the fuel pump is deactivated. Also, when the fuel pressure detected by the fuel pressure sensor becomes equal to or less than an abnormal threshold value, either one or both of the fuel pump and the engine are deactivated. The water jet propulsion boat lowers power consumption, reduces battery size, extends battery life, and lowers costs.

Abstract: A watercraft with a control system includes at least two propulsion units carried by a hull of the watercraft. Each propulsion unit is independently turnable. The watercraft includes a control system arranged to control orientation of the propulsion units. The control system includes a first control mode in which turning of two of the propulsion units is limited to turning through less than an entire range of motion of the two propulsion units, in equal amounts, and in opposite directions relative to a longitudinal centerline of the watercraft.

Abstract: A water jet propulsion watercraft includes a hull, an engine disposed inside the hull, a jet propulsion device arranged to be driven by a driving force of the engine, a water detection unit arranged to detect whether or not the hull is immersed in water, and a control unit arranged to restrict an engine rotational speed. The jet propulsion device is arranged to jet water rearward from a jet port to thereby apply a propulsive force to the hull. The water detection unit includes a water detection chamber arranged such that water around the hull is introduced when the hull is in water, and a water level sensor arranged to detect a water level inside the water detection chamber.

Abstract: An engine in an outboard motor includes a first rotation angle sensing device arranged to sense a rotation angle of a crankshaft and second rotation angle sensing device arranged to sense a rotation angle of an exhaust camshaft. A reverse rotation determination section is arranged to determine an occurrence of a reverse rotation of the crankshaft based on of a rotation angle sensed by the first rotation angle sensing device and a rotation angle sensed by the second rotation angle sensing device. A gear mechanism operation section forceaby shifts a shift gear mechanism into a neutral state when a reverse rotation of the crankshaft is sensed by the reverse rotation determination section. Water is surely prevented from entering the internal combustion engine and can minimize an increase in the manufacturing cost and simplify the maintenance work of the internal combustion engine.

Abstract: A propulsion system for a boat includes propellers rotated by an engine, a transmission mechanism arranged to transmit a driving force of the engine to the propellers in a state that the driving force of the engine is changed to at least one of a gear reduction ratio for low speed and a gear reduction ratio for high speed, and a control unit arranged to output a signal to control a gear shift in the transmission mechanism on the basis of a throttle valve opening of the engine and a speed of the engine and arranged to detect cavitation generated in conjunction with rotation of the propellers on the basis of a gear shift control map. The control unit is arranged to control the output of a signal to the transmission mechanism to change the high speed reduction gear ratio when cavitation is detected. The propulsion system achieves both acceleration and maximum speed at performance levels desired by an operator of a boat.

Abstract: A propulsion system for a boat includes propellers arranged to be rotated by an engine, a transmission mechanism arranged to transmit driving force of the engine to the propellers such that a speed of the driving force of the engine is changed at least with a gear reduction ratio for low speed and high speed, and a control unit arranged to output a signal to control a gear shift in the transmission mechanism on the basis of an amount of lever opening, which is based on operation of a control lever section, and speed of the engine, and the control unit being arranged to detect cavitation generated in conjunction with rotation of the propellers on the basis of a gear shift control map. The control unit is arranged to control output of a signal to the transmission mechanism for changing a reduction gear to that for high speed when cavitation is detected.