Ship propulsion device

1. A ship propulsion device comprising:

a propeller configured to propel a ship;

an engine configured to rotate the propeller;

a clutch configured to transmit revolutions of the engine to the propeller;

an input means configured to input a state of the clutch;

a rotational speed detection means configured to detect a rotational speed of the propeller; and

a control means configured to control operational speed of the engine and the state of the clutch, wherein

the control means operates the engine at a first engine speed when the clutch is an a disengaged state;

the control means, based on the input of the input means, changes the state of the clutch from the disengaged state to a partially engaged state and operates the engine at a second engine speed that is higher than the first engine speed;

the control means, based on a detected rotational speed of the propeller by the rotational speed detection means, operates the engine at an engine speed that is lower than the second engine speed; and

the control means, based on the input of the input means, changes the state of the clutch from the partially engaged state to an engaged state.

2. The ship propulsion device according to claim 1 ,

wherein the control means returns the speed of the engine from the second engine speed to the first engine speed based on the detected rotational speed of the propeller by the rotational speed detection means.

3. The ship propulsion device according to claim 2 ,

wherein the detected rotational speed of the propeller by the rotational speed detection means equals the first engine speed.

4. A ship propulsion device comprising:

a propeller propelling a ship in a predetermined direction;

an engine rotating the propeller;

an input device for inputting and switching between clutch states including a disengaged state, a partially engaged state and an engaged state;

a clutch transmitting rotational force of the engine to the propeller in one of the disengaged clutch state, the partially engaged clutch state and an engaged clutch state;

a rotational speed detection device detecting a rotational speed of the propeller; and

a control device receiving a clutch state from the input device and a detected rotational speed of the propeller from the rotational speed detection device and controlling operational speed of the engine and the state of the clutch,

wherein the control means is configured to:

operate the engine at a first engine speed when the input device designates the disengaged clutch state,

change the clutch state from the disengaged state to the partially engaged state when the input device is switched from the disengaged state to the partially engaged state and operate the engine at a second engine speed that is higher than the first engine speed,

operate the engine at an engine speed that is lower than the second engine speed when the detected rotational speed of the propeller equals a target speed, and

change the state of the clutch from the partially engaged state to the engaged state when the input device is switched from the partially engaged state to the engaged state.

5. The ship propulsion device according to claim 4 ,

wherein the control device returns the speed of the engine from the second engine speed to the first engine speed when the detected rotational speed of the propeller equals the target speed.

6. The ship propulsion device according to claim 4 ,

wherein the target speed equals the first engine speed.