My answer to How long can a boat with a hole in it stay afloat?
Answer by Desmond Last:
Not long if it is a hole which has an area which allows in more water than the bilge pumps can discharge. Boats are fitted with bilge pumps which pump out water from the hull.
An older timber boat will pump out water regularly as the timber swell and move with the changes in water pressure on the hull and temperature variation.
Older Propeller shaft glands are designed to allow a small amount of water to keep the cladding used as the seal from overheating. The water will accumulate in the hull until it is pumped out. It is a good idea to leave a little salt water in the bilge of a timber boat as it prevents the timber frying out.
Should a boat over turn then it is highly likely that the air trapped in the hull will keep it afloat for a considerable time.
Recreational boats left on moorings or berths should always ensure the batteries which power the bilge pump are fully charged with a solar panel or wind generator.
The bilge pumps are actuated by a float switch. When leaving your boat test the switch to make sure the pump is working and leave the pump switch on ‘auto’.
Older boats will tend to block the pump with rubbish make sure the bilge is kept clean and the water intake has a filter fitted.
Commercial boats have bilge pump systems which are tested as part of their seaworthiness requirements.
If you are on a boat which suddenly takes on water the first thing to do is isolate the water intake area, try and block the hole and radio for help or assistance depending on the bilge pumps ability to remove the water.