Jet-propulsion personal watercraft

A jet-propulsion personal watercraft comprising:

• an engine which is configured to generate a driving power for generating a propulsion force to propel the watercraft;
• an engine speed changing system which is configured to be able to change an engine speed of the engine;
• a determiner configured to determine whether or not to execute a control for effectively steering the watercraft at a start of deceleration of the watercraft;
• and
• an engine controller configured to control the engine speed changing system based on information received from the determiner;
• wherein the engine controller is configured to, when the determiner determines that the control for effectively steering the watercraft should be executed, control the engine speed changing system to output a command to lower the decrease rate of the engine speed;
• and
• wherein the engine controller is configured to control the engine speed changing system so that an average decrease rate of the engine speed for 0.3 seconds immediately after the determiner determines that the control for effectively steering the watercraft should be executed is smaller than an average decrease rate of the engine speed for 0.3 seconds immediately after the determiner determines that the control for effectively steering the watercraft should not be executed.

A jet-propulsion personal watercraft comprising:

• an engine which is configured to generate a driving power for generating a propulsion force to propel the watercraft;
• an engine speed changing system which is configured to be able to change an engine speed of the engine;
• a determiner configured to determine whether or not to execute a control for effectively steering the watercraft at a start of deceleration of the watercraft;
• and
• an engine controller configured to control the engine speed changing system based on information received from the determiner;
• wherein the engine controller is configured to, when the determiner determines that the control for effectively steering the watercraft should be executed, control the engine speed changing system to output a command to lower the decrease rate of the engine speed;
• and
• wherein the engine controller is configured to control the engine speed changing system so that an average decrease rate of the engine speed in a time period from immediately after the determiner determines that the control for effectively steering the watercraft should be executed until the engine speed reaches 3000 rpm or lower is smaller than an average decrease rate of the engine speed for 0.3 seconds immediately after the determiner determines that the control for effectively steering the watercraft should not be executed.

A jet-propulsion personal watercraft comprising:

• an engine which is configured to generate a driving power for generating a propulsion force to propel the watercraft;
• an engine speed changing system which is configured to be able to change an engine speed of the engine;
• a determiner configured to determine whether or not to execute a control for effectively steering the watercraft at a start of deceleration of the watercraft;
• and
• an engine controller configured to control the engine speed changing system based on information received from the determiner;
• wherein the engine controller is configured to, when the determiner determines that the control for effectively steering the watercraft should be executed, control the engine speed changing system to output a command to lower the decrease rate of the engine speed;
• and
• wherein the engine controller is configured to control the engine speed changing system to set a time interval during which the decrease rate of the engine speed is maintained to be smaller than a decrease rate of the engine speed immediately after the determiner determines that the control for effectively steering the watercraft should be executed, when the driving power output detector detects that the engine speed is decreased to a fourth threshold higher than an idling engine speed from a time point when the determiner determines that the control for effectively steering the watercraft should be executed.

A jet-propulsion personal watercraft comprising:

• an engine which is configured to generate a driving power for generating a propulsion force to propel the watercraft;
• an engine speed changing system which is configured to be able to change an engine speed of the engine;
• a determiner configured to determine whether or not to execute a control for effectively steering the watercraft at a start of deceleration of the watercraft;
• and
• an engine controller configured to control the engine speed changing system based on information received from the determiner;
• wherein the engine controller is configured to, when the determiner determines that the control for effectively steering the watercraft should be executed, control the engine speed changing system to output a command to lower the decrease rate of the engine speed;
• wherein the engine speed changing system includes an air-intake passage through which air taken in from outside is guided to the engine, a throttle valve configured to substantially open and close the air-intake passage based on an operation amount of an input device, a bypass passage connected to the air-intake passage so as to bypass the throttle valve, a bypass valve configured to substantially open and close the bypass passage, and a bypass valve driving device configured to drive the bypass valve;
• and
• wherein the engine controller is configured to execute valve opening degree control for causing the bypass valve driving device to increase or maintain an opening degree of the bypass valve immediately after the determiner determines that the control for effectively steering the watercraft should be executed.

A jet-propulsion personal watercraft comprising:

• an engine which is configured to generate a driving power for generating a propulsion force to propel the watercraft;
• an engine speed changing system which is configured to be able to change an engine speed of the engine;
• a determiner configured to determine whether or not to execute a control for effectively steering the watercraft at a start of deceleration of the watercraft;
• and
• an engine controller configured to control the engine speed changing system based on information received from the determiner;
• wherein the engine controller is configured to, when the determiner determines that the control for effectively steering the watercraft should be executed, control the engine speed changing system to output a command to lower the decrease rate of the engine speed;
• wherein the engine speed changing system includes an air-intake passage through which air taken in from outside is guided to the engine, a throttle valve configured to substantially open and close the air-intake passage based on an operation amount of an input device, and an actuator configured to apply to the throttle valve a force in a direction to open the throttle valve;
• and
• wherein the engine controller is configured to execute valve opening degree control for causing the actuator to apply to the throttle valve the force in the direction to open the throttle valve immediately after the determiner determines that the control for effectively steering the watercraft should be executed.

A jet-propulsion personal watercraft comprising:

• an engine which is configured to generate a driving power for generating a propulsion force to propel the watercraft;
• an air-intake passage through which air taken in from outside is guided to the engine;
• a throttle valve configured to substantially open and close the air-intake passage;
• a bypass passage connected to the air-intake passage so as to bypass the throttle valve;
• a bypass valve configured to substantially open and close the bypass passage;
• a bypass valve driving device configured to drive the bypass valve;
• a determiner configured to determine whether or not to execute a control for effectively steering the watercraft at a start of deceleration of the watercraft;
• an engine controller configured to control the bypass valve driving device based on information received from the determiner;
• and
• an ignition device configured to ignite an air-fuel mixture in the engine;
• wherein the engine controller is configured to, when the determiner determines that the control for effectively steering the watercraft should be executed, cause the bypass valve driving device to increase or maintain the opening degree of the bypass valve immediately after the determination;
• and
• wherein the engine controller is configured to execute ignition timing control for increasing an advancement angle value of ignition timing of the ignition device, immediately after the determiner determines that the control for effectively steering the watercraft should be executed.