A controller that executes engine output control that a throttle is closed when a boat is navigated at a predetermined speed or higher and the output of an engine is gradually increased up to predetermined output when a steering system is steered right or left at a predetermined angle or more is provided. Thus, an overshoot phenomenon that the engine speed is held at a predetermined engine speed after the engine speed once increases up to the predetermined engine speed or higher when the engine speed is increased in deceleration can be avoided. As a result, the body of the boat can be prevented from sliding laterally to a great extent at the beginning of turning and the turning performance of the body can be enhanced.