An outboard motor engine and a protruding member for use therewith are provided. The outboard motor engine can have a crankshaft whose first end can be connected to a driven member. The protruding member can extend outwardly in the axial direction from a second end of the crankshaft and rotate about an axis with the crankshaft. A flywheel can be fixed on a protruding end side of the protruding member by a tightening member. A drive pulley can be fixed on a base side of the protruding member on the axis. The tightening member can be oriented eccentrically with respect to the drive pulley in the axial direction of the protruding member.