PURPOSE: To obtain both trim adjusting and reversing functions by the same operating mechanism by oscillating a duct vertically within a certain range and further oscillating the duct downward exceeding the fixed range.

CONSTITUTION: When the longitudinal inclination of a boat is detected and an actuator 28a is operated, a duct 31 oscillates vertically against an arm 29 integral with a steering nozzle 28, water jet from the main nozzle 31a of the duct 31 is deflected vertically, and the position of the boat is controlled. When the movable rod 38 of the actuator 28a is delivered exceeding the trim adjusting range, the duct 31 is rotated further downward around a rotation axis 30. At this time, a pin 35 is engaged with an engaging groove 36 formed at a movable arm 34, and the movable arm 34 performs circular motion around a rotation axis 32 against the duct 31. The water jet heading for the main nozzle 31a is obstructed by a movable plate 33, changes its flow direction toward the bow along a reversed duct 31b, and is shifted to backing through the stopping state.