Patent ID: 8092266

Claim:
A marine vessel propulsion unit comprising: an engine; a drive shaft arranged to be rotated by the engine; a propeller shaft to which rotation of the drive shaft is transmitted; a propeller arranged to be rotated together with the propeller shaft; an intermediate shaft arranged on a central rotation axis of the propeller shaft and to transmit rotation between the drive shaft and the propeller shaft; a forward-reverse switching mechanism arranged to switch a rotational direction of the propeller shaft to a forward drive direction or a reverse drive direction; and a shock reduction mechanism including a plurality of spring members arranged to absorb a force in the rotational direction by elastically deforming in the rotational direction when the force in the rotational direction is applied to the intermediate shaft, and a pair of stopper portions arranged to prevent elastic deformations of the plurality of spring members by coming into contact with each other when the elastic deformation amounts of the plurality of spring members reach a predetermined value, the shock reduction mechanism being arranged on the central rotation axis of the propeller shaft; wherein the shock reduction mechanism further includes first and second relative rotation members arranged to rotate relatively in the rotational direction when the force in the rotational direction is applied to the intermediate shaft, and the plurality of spring members are arranged between the first and second relative rotation members and arranged to be compressed in the rotational direction according to relative rotations of the first and second relative rotation members; and the shock reduction mechanism further includes a first housed member housed in the second relative rotation member and arranged to support a first side of each of the spring members, and a second housed member housed in the second relative rotation member and arranged to support a second side of each of the spring members, the first and second housed members are arranged to approach each other according to relative rotations of the first and second relative rotation members, and each of the spring members is arranged to be compressed by the first and second housed members according to approaching of the first and second housed members to each other.