Patent ID: 8419489

Claim:
A propeller unit arranged to be coupled to a propeller shaft of a marine vessel propulsion device, the propeller unit comprising: an inner cylinder arranged to be attached to the propeller shaft; an outer cylinder having a cylindrical shape coaxial with the inner cylinder and including blades fixed on an outer circumferential surface of the outer cylinder; a first driving force transmitting member including a cylindrical elastic member arranged between the inner cylinder and the outer cylinder; a second driving force transmitting member arranged between the inner cylinder or the propeller shaft and the outer cylinder and aligned with the first driving force transmitting member in an axial direction of the outer cylinder; a pair of first engaging portions arranged on the outer cylinder and the first driving force transmitting member and including a protrusion and a groove arranged to mutually engage such that a driving force is transmittable to each other, the protrusion being provided on an inner circumferential surface of the outer cylinder and arranged to protrude inward from the inner circumferential surface of the outer cylinder, and the groove being provided in an outer circumferential surface of the first driving force transmitting member; and a pair of second engaging portions arranged on the outer cylinder and the second driving force transmitting member and arranged such that the second engaging portions are disengaged when a driving force is not transmitted to the propeller shaft, and arranged such that the second engaging portions become mutually engaged in a driving force transmittable manner due to elastic deformation of the first driving force transmitting member when a driving force that is not less than a reference driving force not exceeding a critical load of the first driving force transmitting member is transmitted to the propeller shaft.