Patent ID: 8340847

Claim:
In a navigation control system for a ship including a ship body having an operator seat, and at least one outboard motor containing an engine, the outboard motor has a throttle actuator that controls a throttle opening of the engine and an engine control module that controls the throttle actuator, the ship body is provided with a ship control module connected to the engine control module, a ship velocity detecting unit that generates a ship velocity signal representing a ship velocity of the ship body, a constant velocity navigation commanding unit that generates a constant velocity navigation command, a target ship velocity commanding unit that outputs a target ship velocity command signal, and an operation lever that controls the throttle opening of the engine, the constant velocity navigation commanding unit, the target ship velocity commanding unit, and the operation lever are placed near the operator seat for operation by the operator, the operation lever is provided with a lever operation amount detecting unit that detects a lever operation amount, the ship velocity detecting unit, the constant velocity navigation commanding unit, the target ship velocity commanding unit, and the lever operation amount detecting unit are connected to the ship control module, the ship control module includes a throttle control means that controls the throttle actuator through the engine control module, and the throttle control means includes first computation means that computes a first target throttle opening for a constant velocity navigation control of the ship based on the constant velocity navigation command using at least the ship velocity signal and the target ship velocity command signal, second computation means that computes a second target throttle opening corresponding to the lever operation amount, and selection and output means that selects one having a smaller value of the first target throttle opening and the second target throttle opening and outputs the one as a throttle opening.