A device for monitoring a boat drive, preferably for monitoring a drive battery of a boat drive, includes a first water sensor configured to switch off the boat drive when a first water level is reached, and a second water sensor configured so as to output a water level warning when a second water level is reached.

A device for monitoring a boat drive, preferably for monitoring a drive battery of a boat drive, includes a first water sensor configured to switch off the boat drive when a first water level is reached, and a second water sensor configured so as to output a water level warning when a second water level is reached.

A marine propulsion system for a marine vessel is provided. The system includes an engine effectuating rotation of an output shaft; at least one battery configured to power a load; an alternator having a rotor that is driven into rotation by the output shaft and that outputs a charge current to the at least one battery; and a control system configured to operate the engine in a propulsion mode to rotate a propulsor to propel the marine vessel and a generator mode to charge the at least one battery while the marine vessel remains stationary. The control system is further configured to receive a generator mode command to start the engine in the generator mode; determine whether at least one generator start condition is satisfied; and responsive to a determination that the at least one generator start condition is satisfied, operate the engine in the generator mode.