Buying guide · 6 min read · 9 August 2026
Best Bilge Pumps for Boats
Best Bilge Pumps for Boats
A bilge pump is one of those items nobody thinks about until it matters enormously. Most boats are underpumped, and many automatic installations fail because of the switch rather than the pump. This guide covers sizing, switches and sensible options.
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What to look for
Rated output is optimistic
Quoted litres or gallons per hour are measured at zero head with no hose. Real output through several feet of hose and a skin fitting can be half that or less. Size up accordingly rather than buying to the quoted figure.
Automatic float switch
An automatic pump only works if the switch does. Traditional float switches jam with debris and hair; electronic and field-effect switches have no moving parts and tend to be more reliable. Whichever you use, test it regularly by lifting the float or flooding the bilge slightly.
Two pumps, not one
Best practice is a small automatic pump low down to handle routine seepage, plus a larger high-capacity pump higher up for emergencies. One pump doing both jobs tends to cycle constantly and wear out.
A manual pump as backup
A manual diaphragm pump works with a flat battery and can shift a lot of water. Many coding regimes require one on commercial vessels, and every boat should carry a bucket regardless.
Wiring and fusing
Automatic pumps need a permanent live feed so they work with the master switch off, properly fused, with marine-grade tinned cable and connections above the waterline. A pump wired through the master switch is useless when it is most needed.
Options worth considering
Listed alphabetically by suitability rather than ranked. We research specifications and reputation; we have not tested these ourselves.
1.Rule-Mate 500 automatic bilge pump
The common defaultA very widely used range of submersible pumps in various capacities, with automatic versions available.
- ✓Available from small to high capacity
- ✓Widely stocked, easy to replace
- ✓Automatic and manual versions
2.Whale Orca / Supersub
Low-profile bilgesA UK manufacturer whose low-profile pumps suit shallow bilges where a conventional pump will not sit.
- ✓Very low profile options
- ✓UK brand with good spares availability
- ✓Suits shallow or awkward bilges
3.Attwood Sahara
Integrated automatic unitA pump with an integrated automatic switch, simplifying installation on smaller boats.
- ✓Built-in automatic switching
- ✓Simple single-unit installation
- ✓Suits smaller craft
4.Johnson Pump bilge range
Solid mid-range choiceA long-established marine pump manufacturer with a broad range of capacities.
- ✓Range of sizes and duties
- ✓Good reputation for reliability
- ✓Spares generally available
5.Whale Gusher 10 Mk3 manual pump
Essential backupA manual diaphragm pump that works without power and shifts serious volume.
- ✓Works with a flat battery
- ✓High output for a hand pump
- ✓Often required for commercial coding
In short
Fit more capacity than you think you need, use a reliable switch, wire it permanently live and fused, and test it every time you go afloat. And carry a bucket.
Frequently asked questions
What size bilge pump do I need?+
Bigger than the quoted figure suggests. Rated output is measured at zero head with no hose, and real-world output through hose and a skin fitting is often half that. Many boats fit a small automatic pump for seepage plus a larger emergency pump higher in the bilge.
Do I need an automatic bilge pump?+
For any boat left on a mooring, yes. It handles rainwater and seepage between visits. Make sure it is wired to a permanently live, fused feed so it works with the master switch off, and test the float switch regularly since switch failure is the common failure mode.
Should I have a manual bilge pump as well?+
Yes. A manual diaphragm pump works with a flat battery or failed electrics, which is exactly when you are likely to need it. Commercial coding regimes often require one, and every boat should carry a bucket too.
Why do bilge pump float switches fail?+
Traditional float switches have moving parts that jam with debris, oil and hair from the bilge. Electronic or field-effect switches have no moving parts and tend to be more reliable, though they are not immune to fouling either.
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