US Patent 9061751 Marine propulsion device

A marine propulsion device includes a motive force transmission system, a propeller shaft, a housing section, and a clutch. The motive force transmission system includes a crank shaft and a drive shaft which transmits a motive force from the crank shaft. The propeller shaft transmits the motive force from the drive shaft. The housing section houses the motive force transmission system. The clutch is attached between the motive force transmission system and the housing section. The clutch permits relative rotation between the motive force transmission system and the housing section by opening a connection between the motive force transmission system and the housing section during normal rotation of the motive force transmission system. The clutch prevents relative rotation between the motive force transmission system and the housing section by connecting the motive force transmission system and the housing section during a reverse rotation of the motive force transmission system.