Marine propulsion system, control method therefor, and marine vessel

A marine vessel comprising:

• a hull;
• and
• a marine propulsion system including:
• a first propulsion device that is steerable and located at a stern of a hull;
• a second propulsion device that is steerable and located in front of the stern;
• and
• a controller configured or programmed to define and function as:
• an obtaining unit to obtain information about a propulsion force of the first propulsion device in a forward direction, information about a propulsion force of the first propulsion device in the backward direction, and information about a propulsion force of the second propulsion device;
• a determination unit to determine when to cause the first propulsion device during a lateral motion of the hull to generate a propulsion force in a direction in a first range including a component in the forward direction, and when to cause the first propulsion device during the lateral motion of the hull to generate a propulsion force in a direction in a second range including a component in the backward direction based on the information about the propulsion force in the forward direction of the first propulsion device, the information about the propulsion force in the backward direction of the first propulsion device, and the information about the propulsion force of the second propulsion device obtained;
• and
• a storage processor to store a content determined by the determination unit in a storage medium as determination information;
• wherein
• the determination unit is configured or programmed to:
• compare a first difference between a minimum value of the propulsion force in the forward direction of the first propulsion device and a maximum value of the propulsion force of the second propulsion device with a second difference between a minimum value of the propulsion force in the backward direction of the first propulsion device and the maximum value of the propulsion force of the second propulsion device;
• and
• determine to cause the first propulsion device to generate the propulsion force in the direction in the first range when the first difference is less than the second difference, and to cause the first propulsion device to generate the propulsion force in the direction in the second range when the second difference is less than the first difference;
• and
• the controller is configured or programmed to control a steering angle of the first propulsion device and a steering angle of the second propulsion device based on the determination information.

A control method for a marine propulsion system including a first propulsion device that is steerable and located at a stern of a hull and a second propulsion device that is steerable and located in front of the stern, the control method comprising:

• obtaining information about a propulsion force of the first propulsion device in a forward direction, information about a propulsion force of the first propulsion device in the backward direction, and information about a propulsion force of the second propulsion device;
• determining when to cause the first propulsion device during a lateral motion of the hull to generate a propulsion force in a direction in a first range including a component in the forward direction, and when to cause the first propulsion device during the lateral motion of the hull to generate a propulsion force in a direction in a second range including a component in the backward direction based on the information about the propulsion force in the forward direction of the first propulsion device, the information about the propulsion force in the backward direction of the first propulsion device, and the information about the propulsion force of the second propulsion device obtained;
• storing a content determined in a storage medium as determination information;
• and
• controlling a steering angle of the first propulsion device and a steering angle of the second propulsion device based on the determination information;
• wherein
• the determining includes:
• comparing a first difference between a minimum value of the propulsion force in the forward direction of the first propulsion device and a maximum value of the propulsion force of the second propulsion device with a second difference between a minimum value of the propulsion force in the backward direction of the first propulsion device and the maximum value of the propulsion force of the second propulsion device;
• and
• determining to cause the first propulsion device to generate the propulsion force in the direction in the first range when the first difference is less than the second difference, and to cause the first propulsion device to generate the propulsion force in the direction in the second range when the second difference is less than the first difference.