To provide an engine output control device for a water jet propulsion boat enabling a navigator to naturally steer and stop the boat even in OFF operation of a throttle.

A control unit 34 starts the lowering control of engine speed when the closing state of the throttle opening over a prescribed value is detected from the signal from a throttle opening detection sensor 23, and the steered state is detected from the signal from a steering switch 24, and changes the lowering control rate of engine speed when the moderated engine speed is smaller than a prescribed engine speed in the engine speed control. The averaging treated engine speed is a value calculated by multiplying the change of engine speed for a prescribed time by the resistance coefficient of the boat.