Abstract: A bilge pump switch apparatus for activating and deactivating the bilge pump of the vessel in response to predetermined water levels in the bilge area comprising a housing defining a chamber therein and provided with a fluid port for receiving and discharging bilge water, a mercury tilt switch suspended within the chamber and being responsive to tilting for opening and closing a circuit including a battery, the mercury tilt switch and the bilge pump, and a float responsive to the water level in the chamber for positioning the mercury tilt switch in its normally open position and its normally closed position.