The Battle of the Bilge

Captain Toby

Captain Toby on Bilge Pumps

The humble bilge pump is rather like a smoke detector in your house – we all know we need it, but never pay any attention to it in the hope that it will work in the unlikely event it is ever called upon to provide service.

Bilge pumps were an urgent requirement in the days of wooden boats because nearly all wooden boats leak. Thankfully, with today’s modern boat building materials, the concern of bilges full of seawater is largely diminished and forgotten, but that water still has a way of creeping in.

There are two ways water is getting into your boat:

    1. THROUGH the hull – this might be through a faulty seacock or skin fitting – or even an old-fashioned leak through the hull.
    2. ON the hull – usually, rainwater that has not drained away through clogged drain holes, but could be water coming over the hull in bad weather. Even classic mistakes like leaving the hose running unattended while washing down the boat or filling water tanks can lead to excess water in the bilges.

When was the last time you visually checked your bilges? Most of us just rely on an automatic bilge pump located out of sight in the lowest part of the boat. This pump is often neglected, sitting in a puddle of oily water and algae.

If you’re on the boat and if your ankles are getting wet, you are going to notice and do something about it. Even if the bilge pump is not working, you can always rely on the old sailor’s adage “there is no more effective bilge pump than an empty bucket in the arms of a frightened man.”

The perfect storm happens when the boat is unattended, which is probably over 90% of the time. Water is coming in at a faster rate than the bilge pump can expel it and eventually the battery starts to die – and you are blissfully unaware of all of this. The water level starts rising in the bilges, and you are now at the mercy of the reliability of an automatic switch on your bilge pump.

These float switches are usually built-in, but older types may have a separate float switch located next to the bilge pump. There are at least 5 different types of bilge pump float switches – and they can all fail.

A standard bilge pump should be connected to permanent power to a fully charged, dedicated battery. It will pump 750 gallons per hour. In reality, with gravity issues, it may be nearer half that, but if you think about it, that could be around six gallons a minute. That is a lot of water. Depending on the amperage of the bilge pump you can roughly figure out how long that dedicated 100amp hour battery is going to last, but we are talking hours here not days.

Here are some simple tips to give you peace of mind:

  • It is good seamanship to check your bilges every time you get on board. You will not be expecting to see any water, but if you do, you will be glad you checked and are getting ahead of the problem.
  • Before you start your engine, turn on the bilge pump on the manual switch and listen to see if it is working – and if it is pumping out any water over the side.
  • Do the same just before you leave your boat – but don’t forget to switch back on to “Auto!”
  • Check your automatic bilge pump. Test it out. Put a hose in the bilge and fill up with fresh water. What happens?
  • Keep your bilges clean! Rinse them out and degrease them. Dry them out and then vacuum until spotless. Your bilge pump will thank you with better service.
  • A little engine oil goes a long way to making a mess. Take a look at putting in one of those oil-absorbing bilge sponges.

Toby Kilner is the Head Technician for Boat Fix with over 30 years of 24/7 experience of diagnosing and fixing mechanical problems at sea.

Over 60% of Boat Fix alarms are from low battery voltage.

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