PURPOSE: To recycle the hither to unused pressure and flow of water as energy after it is thrust out by a propeller, by using a propulsion assistor.

CONSTITUTION: A rotor equipped with a machine 5 shaped to receive water pressure has its rotating shaft 6 stretched between the ends of rotor supports 2, at a propeller 3, the pressure and flow 4 of water, and the stern 1. A bevel gear 10' is provided at one side of the rotating shaft 6, a shaft 11' is provided at a mating bevel gear 10, and an universal joint 12 is provided in the center of a shaft 11. The end of the shaft 11 is made to serve as two shafts by a gear changer 18, with another power source shaft 16 attached to one of the two shafts and a gear 13 to the other shaft. A gear 135 is linked to a propeller shaft gear 14 by a chain 15. A hydraulic cylinder 17 is attached to the stern 1 and the rotor support 2.