Abstract: A control method for a watercraft is used for the watercraft including a device that requires authentication of identification information for activation, and has reading processing, authentication processing, and activation permission processing. In the reading processing, the identification information is read by each of plural reading sections, each of which is mounted on a hull of the watercraft and can read the identification information. In the authentication processing, the identification information, which is read in the reading processing, is authenticated by referring to authentication information. In the activation permission processing, in the case where the identification information that is read by any one of the plural reading sections is successfully authenticated, the device is brought into an activatable state.

Abstract: A ship propulsion device includes three or more propulsion units, a malfunction detection unit, and a control unit. The control unit is configured to control the three or more propulsion units. The three or more propulsion units are disposed with left-right symmetry. Based on a malfunction detected in any one of the three or more propulsion units by the malfunction detection unit while the three or more propulsion units are operating, the control unit is configured to stop the propulsion unit in which the malfunction is detected, and, on a left side and a right side of a hull, stop at least one propulsion unit of the three or more propulsion units disposed on the side opposite from the side on which the propulsion unit in which the malfunction is detected is disposed.