Marine propulsion system with water detecting sensors

A marine propulsion system is provided with a liquid detector located within a cooling passage of the cooling system of an engine. Conductivity sensors, or other types of liquid sensors, provide signals representative of the absence or presence of water at particular locations within the cooling system. The signals are used to energize and de-energize various annunciators on a display panel to inform the operator of a marine vessel of the status of a draining procedure. When all of the annunciators properly indicate the absence of water within strategic locations of the cooling system, the marine vessel operator can be assured that the draining procedure has been effectively completed.