To provide a ship propulsion unit that can easily control engine and electric motors and suppress exhaust gas and noise when going astern, and to provide its operating method.

A ship propulsion unit 10 includes a maneuvering lever 46 for indicating the kind of operational modes as well as the magnitude of output of a drive source, and a controller 42 for setting a propeller drive mode depending on an indication by the maneuvering lever 46. When an astern mode is indicated by the maneuvering lever 46, the controller 42 sets the propeller drive mode at a first mode in which a propeller 12 is reversely rotated by an electric motor 16 and the magnitude of output of the electric motor 16 is adjusted depending on an indication from the maneuvering lever 46. The maneuvering lever 46 is rotatable, and can indicate the kind of operational modes and the magnitude of output of the drive source.