Patent ID: 8105122

Claim:
A propulsion device for a marine motor, comprising: a gear case provided in a lower part of the marine motor and receiving a propeller shaft extending substantially horizontally therein; a drive shaft passed vertically in the gear case and having an upper end connected to a crankshaft of an engine in a torque transmitting relationship and a lower end received in the gear case and fitted with a drive bevel gear; a pair of driven bevel gears supported by the gear case in a freely rotatable manner around an axial line of the propeller shaft and meshing with the drive bevel gear from mutually opposite directions; a clutch member engaged rotationally fast and axially slidably by the propeller shaft, and provided with engagement teeth configured to engage one of the driven bevel gears at a first axial position and the other driven bevel gear at a second axial position; a hydraulic actuator defining two chambers and having an output member that is actuated in a desired direction depending on which of the two chambers hydraulic pressure is supplied, the output member being connected to the clutch member via a force transmitting member in such a manner that the clutch member may be selectively actuated to each of the first and second axial positions; a shift member engaging the force transmitting member in such a manner that a movement of the shift member causes the clutch member to be selectively actuated to each of the first and second axial positions; a hydraulic source; and a valve provided in association with the shift member so that hydraulic fluid from the hydraulic source is supplied to a selected one of the two chambers depending on a direction of a movement of the shift member so that the hydraulic actuator provides an assisting force for an actuation of the clutch member in a direction to assist an effort to actuate the clutch member by using the shift member, wherein the force transmitting member comprises a slide rod and a rack member, the slide rod having a rear end coaxially connected to a front end of the propeller shaft and the rack member extends forward in the axial direction from the front end of the slide rod and is formed with a rack, and wherein the shift member comprises a shift rod extending vertically in the gear case and is fitted with a pinion in a lower end thereof which meshes with the rack, the valve being configured as a rotary valve which is actuated by an angular movement of the shift rod.