PURPOSE: To lessen vibration to be generated by a propeller by installing a metal ring body through an elastic material so as to produce rotation with the rotation of a propeller shaft.

CONSTITUTION: To damp lateral vibration of a propeller shaft, a marine propulsion device 11 has a damper 51 fixed to the front of a propeller 47. The damper 51 includes a means for resiliently connecting the propeller shaft 37 to an annular body 53. An elastic ring 59 is installed between the propeller shaft 37 and the annular body 53. The ring 59 has an inner surface 61 joined to the outer surface of the propeller shaft 37 and an outer surface 63 joined to the inner surface 57 of the annular body 53.