How to Choose a Bilge Pump

Use these tips to make sure you've got the best bilge pump for your boat.

How to Choose a Bilge Pump
Mount pumps level, or with the outlet facing up, to allow air to escape the impeller chamber and prevent air locks.Whale Pumps

A bilge pump is an essential piece of boating equipment. When shopping for a new boat, take the time to compare the bilge-pump installations aboard the boats on your short list. I have found this to be a good barometer of the overall care a boatbuilder takes in rigging and equipping a new boat. While there's more to a great bilge-pump installation than just what's here, check out the following tips.

American Boat and Yacht Council standards require the pump be accessible to remove debris or clean its intake screen. This seems logical, but I have found that it is less common than logic — and ABYC compliance — suggests.

Sometimes pumps that need to be located beneath engines can be mounted to a removable board that slides out for service. In other instances, only those with long arms can reach the pump through cockpit sole hatches or deck plates. In such cases, a pump that can be installed in the open might be used instead, with an intake hose ­running to the deep part of the bilge. Strainers (aka strum boxes) for the working end of such hoses indicate a builder who is concerned about bilge-pump reliability.

Bigger is better. The largest-capacity pump that will fit in the area is the best way to go. A big reason for this logic is that the rated capacity of the pump almost always far exceeds the actual performance.

The specific reasons for this will vary with individual installations. But variables include the height that water must be lifted to be discharged (aka head); the diameter of the hose used and whether it is smoothbore or corrugated; the use of check valves and 90-degree fittings; and voltage drop. A bilge pump is not an emergency pump designed to stem catastrophic flooding. But it should evacuate water as quickly and efficiently as possible, which can prevent catastrophe or buy boaters time in the event of a catastrophe.

Check Valves
A check valve may be installed in the discharge line of a bilge pump. It can prevent cycling of the pump. (Water in the hose when the pump shuts off runs back into the bilge, floats the switch and turns the pump back on.) A check valve can also prevent back-flooding through the ­discharge fitting if the fitting becomes submerged as it might when launching a boat off a trailer at a steep ramp, or if aground and listing. But check valves can clog with salt and debris, so they must be accessible, and boaters should make it a habit to inspect these for proper operation regularly.

Quick Tip: Ideally, bilge pumps should be mounted 2 to 3 inches from a vertical bulkhead or stringer to avoid cavitation or air lock.