A dog clutch mechanism incorporated in an outboard motor includes a sliding clutch dog member splined to a propeller shaft and having recesses on each end face thereof, and a row of gear teeth formed on an end face of each of a pair of driven gears rotatably mounted on the propeller shaft. Each of the recesses has a bottom surface stepped to provide a corner edge at a stepped portion thereof. Each of the gear teeth has a beveled surface formed at a rear edge as viewed from a rotating direction of the driven gear. When the gear teeth are in mesh with the recesses of the clutch dog member, the corner edge of the stepped bottom surface of each recess is in contact with the beveled surface of the mating gear tooth.