A propeller unit for a marine vessel propulsion device includes an inner cylinder arranged to be fixed to the propeller shaft, an outer cylinder, a first driving force transmitting member, and a second driving force transmitting member. The propeller unit for marine vessel propulsion device further includes a pair of first engaging portions, and a pair of second engaging portions provided on the outer cylinder and the second driving force transmitting member. The pair of second engaging portions are arranged such that the mutual engaging of the respective second engaging portions is disengaged when a driving force is not transmitted to the propeller shaft and are arranged such that the respective second engaging portions become mutually engaged in a driving force transmittable manner by elastic deformation of the first driving force transmitting member when a driving force that is not less than a reference driving force is transmitted to the propeller shaft.