PURPOSE: To ensure the winding and the releasing of a mooring rope for a float body on the basis of a simple structure by using high-pressure gas cracked from monoliquid fuel to push out operation liquid for operating a hydraulic motor and thereby operating a winch connected to the hydraulic motor.

CONSTITUTION: When a valve 15 is opened by the command from a mother ship, monoliquid fuel is pushed into a gas generator 10 from its tank 11 by the gas pressure in a high-pressure gas tank 16, and cracked into a high pressure gas by a catalyzer in the gas generator 11. Then, this high-pressure gas pushes the oil in one of operation liquid tanks 6 and 6', that is, the oil selected by a control valve 13 via the control valve 13 and a pipe 12, and drives a hydraulic motor 5 via pipes 7, 7a, 7', 7a', and others for rotating a winch shaft 4 connected thereto in a direction to wind or release a mooring rope. Devices illustrated as 8 and 9 are direction-change control valves.