It comes on automatically when it is submerged it has a float switch in it. The bilge forms the joint where two sides of a ship or boat connects.
Bilge Care Amp Maintenance Made Easy Partsvu Blog
How does a bilge pump work on a boat. The main goal of a bilge pump is to clear out water from the bilge area of your boat. Water gets in there when it splashes into the boat or when something bad happens like a leak in the hull or you forget to put the plug in at the launch ramp. Ship or boat owners install bilge pumps at the lowest possible level of the ship below the sea surface in an area called the bilge. The pump will help you in determining whether there is any licking taking place in the boat or not. It can also be turned on manually via the dash. The primary job of most bilge pumps on most boats is to clear nuisance water from the bilges packing gland drips spray from an errant wave etc.
Bilge pumps are essentially electrical water pumps that are wired into the ships main electrical system or to a marine battery. The main job of bilge pumps in many boats in clearing different nuisances in the water. This is vital for ensuring that your boat can stay afloat. There are pumps bought together with the ship and with time they end up wearing out and in such cases you will need to purchase a new bilge pump. It is even more important in an emergency when you are trying to reduce the amount of water your boat might start to take on. Its just a pump for getting water out of your bilge.