Boat propulsion system, control device thereof, and control method

A control device of a boat propulsion system, the control device comprising:

• a power source arranged to generate a rotational force;
• a propulsion unit including a propeller operated by the rotational force of the power source so to generate a propulsive force;
• a rotational speed detection section arranged to detect a rotational speed of the propeller;
• a shift mechanism disposed between the power source and the propulsion unit and arranged to change between a first shift position, neutral, and a second shift position to transmit the rotational force of the power source to the propulsion unit as a rotational force in a rotational direction opposite to that of the first shift position;
• an actuator arranged to drive the shift mechanism;
• a control lever to which an accelerator opening and a shift position are input by an operation of an operator;
• a shift position detection section arranged to detect the input shift position;
• and
• an accelerator opening detection section arranged to detect the input accelerator opening;
• wherein
• the actuator is arranged to select the shift position on the basis of the detected shift position and to control an output of the power source on the basis of the detected accelerator opening;
• and
• the actuator is arranged to maintain the first shift position until the rotational speed of the propeller becomes equal to or lower than a predetermined rotational speed and then to change to the second shift position when the control lever is operated such that the shift position detected by the shift position detection section is changed from the first shift position to the second shift position, and such that the absolute value of the accelerator opening varying speed obtained by differentiating the accelerator opening becomes equal to or larger than a predetermined value.

A method of controlling a boat propulsion system, the method comprising the steps of:

• generating a rotational force so as to rotate a propeller;
• detecting a rotational speed of the propeller;
• providing a shift mechanism to shift between a first shift position, neutral, and a second shift position that transmits the rotational force to the propeller as a rotational force in a rotational direction opposite to that of the first shift position;
• detecting a shift position of the shift mechanism;
• detecting an accelerator opening;
• and
• controlling an actuator so as to maintain the first shift position until the rotational speed of the propeller becomes equal to or lower than a predetermined rotational speed and then to change to the second shift position when a control lever is operated such that the detected shift position is changed from the first shift position to the second shift position, and such that the absolute value of the accelerator opening varying speed obtained by differentiating the accelerator opening becomes equal to or larger than a predetermined value.