PURPOSE: To read a jump-up angle of a propeller unit in a hull, by providing an interlocking means for interlockng an angle detecting part which follows a turning of the propeller unit around a tilt shaft, and an angle reading part provided in the hull.

CONSTITUTION: When an oil pressure cylinder 50 is expanded or contracted by switching oil pressure supplied to an oil chamber of the cylinder 50, by a control valve, both a steering fork 18 and a propeller unit 16 are turned clockwise or counterclockwise around a tilt shaft 24, and a projecting part 90 is also turned together with them. Therefore, a rod 66 being a part of an angle detecting part 88 moves, following the turning of the propeller unit 16, and a lever 100 of an angle reading part 92 is pressed against the end part of the inboard side of this rod 66, and is turned as the rod 66 moves. When the lever 100 is turned, a rotary shaft 98 is also rotated, a rotating angle of the propeller unit 16 is converted to an electric signal by a sensor 96, and a jump-up angle of the propeller unit is displayed by a trim-meter.