Marine Bilge Pumps

Water finds its way into every hull. A working marine bilge pump is what sends it back out. Shop 12V and 24V bilge pumps from 200 to 4,000 GPH, including automatic pumps with built-in sensors, from Rule, Johnson Pump, Attwood, Whale, Jabsco and more. Not sure what size you need? Open our buying guide below.

+ Bilge Pump Buying Guide: Sizing, 12V vs 24V, Installation and FAQs

How to Choose a Bilge Pump for Your Boat

Three numbers decide it: flow, voltage and how the pump switches on. Get those right and the brand is a matter of taste.

How to choose a bilge pump infographic: size by real flow, match 12V or 24V, pick the switch type, and primary pump GPH by boat length

1. Size by Real Flow, Not the Box

The GPH on the label is measured at zero head and full voltage. Your boat offers neither. Every foot of lift, every bend in the hose and every bit of voltage drop cuts real output, often by a third or more. Buy above what you think you need.

Boat length	Primary pump (rated GPH)	Backup / high-water pump
Under 20 ft	500–800 GPH	Optional manual pump
20–30 ft	800–1,500 GPH	1,500–2,000 GPH
30–40 ft	1,500–2,000 GPH	2,000–3,700 GPH
40 ft and up	2,000+ GPH per compartment	3,700–4,000 GPH high-water pump

Two pumps beat one big one. Mount the primary low to handle rain and drips; set a larger high-water pump a few inches higher, wired to its own alarm.

2. Match Your Voltage: 12V or 24V Bilge Pumps

Most boats under 35 feet run 12V. Many larger yachts, sportfishers and commercial boats run 24V. A 12V pump on a 24V system burns out. A 24V pump on 12V barely turns.

Running 24V? You still get choices. We stock 24V bilge pumps from Rule, Commodore, BILGE-B-DRY, Whale and Johnson, from compact automatic pumps to 2,000+ GPH units. Filter the products below by voltage, or send us your boat's specs and we'll pick one.

3. Pick How It Turns On

Automatic bilge pumps sense water through electronic sensors or periodic test cycles. No separate switch to fail. Great for small boats and tight bilges.
Non-automatic pumps pair with a float switch or electronic water sensor. Better for deep bilges and high-capacity setups because you choose where the switch lives.
Manual pumps need no power at all. Keep one aboard as the last line of defense.

Installation Tips From Our Service Team

Use smooth-bore hose sized to the pump outlet. Ribbed hose kills flow.
Keep the discharge run short and loop it high above the waterline, with an anti-siphon loop or check valve where the manufacturer allows.
Wire the pump with marine-grade tinned wire sized for the run, sealed heat-shrink connectors and a fuse at the source.
Wire the float switch to the battery directly (fused) so the pump works with the main switch off.
Clean the strainer base every season. Hair, zip ties and sawdust jam more pumps than anything else.

Want the deep dive? Read our step-by-step guide to choosing a bilge pump and our complete marine bilge system guide.

Bilge Pump FAQs

What size bilge pump do I need?

Most boats in the 20–30 foot range use an 800–1,500 GPH primary pump and a larger backup. Size up from the label rating because real-world flow drops with lift and hose length.

Is an automatic bilge pump better than a float switch?

Automatic pumps are simpler to install and have fewer parts. A separate float switch gives you more control over the pump-on height and suits deep or large bilges.

Can I use a 12V bilge pump on a 24V boat?

No. Match the pump to your system voltage. A 12V pump on 24V will overheat and fail.

How often should I replace a bilge pump?

Test it monthly and inspect it every season. Many owners replace primary pumps every three to five years as cheap insurance, or immediately if the motor sounds rough or draws high amps.