How do I choose a reliable bilge pump for my boat?

Choose a bilge pump by the flow it delivers through your boat's discharge hose, its resistance to blockage and how easily you can inspect and test it. For dependable protection, fit an automatic electric pump and an independent manual pump, and consider a separate electric pump mounted higher in the bilge, plus a high-water alarm.

Inspect the bilge and discharge

Before buying, lift the sole boards and inspect the lowest collecting point, existing pump, wiring and outlet hose. A bigger pump achieves little if its intake sits above the water or the hose has kinks, restrictions or blockages.

• Measure the available footprint and check access: you must be able to remove the strainer and reach the automatic switch.
• Measure the vertical lift from the pump to the discharge point, plus hose length and internal diameter.
• Check the supply voltage: usually 12V on smaller boats, sometimes 24V on larger yachts.
• Identify separate bilge compartments; water trapped behind a watertight bulkhead cannot reach a pump elsewhere.

Keep paper labels, cable offcuts, hair and wood debris out of the bilge. Even carefully built yachts can shed sawdust from hidden pockets. A blocked strainer can defeat an otherwise sound pump.

Check flow at working height

The large gallons-per-hour figure on a centrifugal pump usually describes favourable test conditions, often with little or no lift. Read the manufacturer's performance curve at your installation's discharge height, then allow for losses through the hose, bends and fittings. Check whether the rating uses US or imperial gallons: 1,000 US gallons per hour is about 63 litres per minute.

For an ordinary cruising boat of 8 to 11 metres, start by comparing automatic pumps rated at around 1,000 to 1,500 US gallons per hour. This is a shopping guide, not a universal minimum: bilge layout, operating area and the manufacturer's installed-flow figures matter more than boat length alone.

Where space allows, fit a small pump low in the bilge for everyday water, with a larger pump higher up for rising water. Give the second pump its own switch and separately protected circuit, preferably with its own discharge.

Factory installations show how these duties differ. Hallberg-Rassy documentation lists routine electric pumps at 16.3 litres per minute, manual pumps at around 90 to 105 litres per minute and separate emergency pumps at 252 litres per minute, depending on the model. These are manufacturer-rated capacities, not guaranteed installed outputs. Ordinary bilge pumps are not designed for damage control; finding and stopping the leak remains essential.

Choose serviceable pumps and controls

For a shallow bilge with easy access, a submersible centrifugal pump is usually a straightforward, economical choice. Rule, Johnson Pump and Attwood are established names; compare their removable strainers, replacement switches and published performance data. These pumps generally need water around the intake and should not be expected to lift water through a suction hose.