Why Your Bilge Pump Matters
A bilge pump is one of the most important safety systems on your boat. It keeps your bilge — the lowest part of the hull — dry by removing water that enters through rain, spray, or a slow leak. When it fails, the consequences can range from minor damage to a sunken boat.
The good news: modern bilge pumps are reliable, affordable, and easy to install. Choosing the right one for your boat size and use case takes just a few minutes of research — which is exactly what this guide is for.
Types of Bilge Pumps
Submersible Electric Pumps
The most popular type. These sit directly in the bilge water and pump it overboard. Most modern boats have at least one submersible pump as the primary bilge pump. They're available in 12V and 24V versions and can move anywhere from 500 to 4,000+ gallons per hour (GPH).
Automatic vs. Manual
Automatic pumps have a float switch that activates when water reaches a certain level. This is critical — you want your pump working even when you're away from the boat or asleep at anchor. Always choose automatic for your primary pump.
Manual pumps are operated by hand and are required as a backup on most vessels. They don't depend on your boat's electrical system, making them a critical safety backup when the engine or batteries are dead.
Centrifugal vs. Diaphragm Pumps
Centrifugal pumps (most submersible pumps) move large volumes of water quickly but can't handle debris well and can't run dry.
Diaphragm pumps handle debris and can run dry without damage. Great for pumping out compartments with debris or for use as a primary pump in boats with wood chips or organic matter in the bilge.
How to Size a Bilge Pump
The general rule: choose a pump rated for at least twice the volume you think you'll need. Water flows in faster than you expect during an emergency.
- Under 20 ft: 500–750 GPH submersible pump
- 20–26 ft: 1,000–1,500 GPH
- 26–32 ft: 2,000–2,500 GPH
- 32–40 ft: 3,500+ GPH (consider two pumps)
- Over 40 ft: Multiple pumps + high-capacity primary
Key Features to Look For
- Amperage draw: Lower amps = less battery drain. Look for high GPH with low amp draw.
- Debris handling: Can it pass small debris without clogging? Look for "strum box" compatibility.
- Automatic switch quality: Electronic float switches are more reliable than mechanical ones in the long run.
- Installation ease: Most pumps use ¾" or 1" hose. Confirm fitting compatibility before buying.
Installation Tips
- Mount the pump at the lowest point in the bilge where water collects
- Use a strum box (filter basket) to keep debris from clogging the impeller
- Wire with properly rated marine-grade wire — bilge is a high-moisture environment
- Always include a manual override switch at the helm
- Test it before every season by pouring water into the bilge
Maintenance
Bilge pumps are "set it and forget it" — until they're not. Check yours every spring:
- Clean the strainer/strum box of debris
- Test the float switch manually
- Check wire connections for corrosion
- Run the pump and confirm water is actually coming out the discharge hose
A bilge pump that's never needed is money well spent. Don't wait for an emergency to discover yours isn't working.
Browse GetBoatParts' full selection of bilge pumps and marine safety equipment.
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