A marine outboard motor having an internal combustion engine is provided. The internal combustion engine includes an engine block having at least one cylinder and a valve train comprising a cam, a valve assembly including a valve spring, a roller finger follower, and a pivot post. The pivot post extends from a fixed body of the engine block and defines a contact surface about which the roller finger follower pivots when deflected by the cam during use. The pivot post is moveable relative to the fixed body in a first longitudinal direction (A) against the action of the valve spring. A removable shim is disposed between the fixed body and a portion (182) of the pivot post to space the pivot post from the fixed body in the first longitudinal direction (A) and thereby reduce an amount of lash between the cam and the roller finger follower. The removable shim is dimensioned to fit at least partly around a shaft portion of the pivot post.