How to Choose the Right Bilge Pump for Your Boat:
A reliable bilge pump is one of the most important pieces of safety equipment on any boat. Whether you operate a small fishing boat, a center console, a pontoon, or a larger offshore vessel, having the right bilge pump can make the difference between a manageable amount of water in the bilge and a serious emergency.
But with so many options available, choosing the right marine bilge pump isn't always straightforward.
Should you choose a 500 GPH, 800 GPH, 1,100 GPH, or 2,000 GPH pump? Is an automatic bilge pump better than a manual model? Do you need a separate float switch? And how many bilge pumps should your boat have?
In this guide, we'll explain what to look for when selecting a bilge pump, how to determine the right pumping capacity, and which features matter most when choosing a pump for your boat.
1. Understand Bilge Pump Capacity: What Does GPH Mean?
The first specification you'll encounter when shopping for a bilge pump is GPH, which stands for gallons per hour.
GPH indicates how much water a pump can theoretically move in one hour under specified test conditions. Common marine bilge pump capacities include:
- 500 GPH: Often suitable for smaller boats and limited bilge spaces.
- 750–800 GPH: A practical option for many small to mid-sized recreational boats.
- 1,000–1,100 GPH: Provides greater pumping capacity for larger bilge spaces and additional water-removal capability.
- 1,500 GPH: A higher-capacity option for larger vessels or installations requiring greater pumping capability.
- 2,000 GPH and above: Designed for installations where substantial pumping capacity is needed
One important consideration: A pump's advertised GPH rating is not necessarily the amount of water it will move once installed.
Actual output decreases as water must travel through hoses, fittings, elbows, and vertical discharge runs. A long or restrictive discharge hose can significantly reduce pump performance.
Our recommendation: Don't select a bilge pump based solely on the size of your boat. Consider the volume of the bilge, potential sources of water intrusion, discharge hose length, and the consequences of a pump failure.
2. Automatic vs. Manual Bilge Pumps: Which Is Better?
One of the most important decisions when purchasing a marine bilge pump is whether to choose an automatic or non-automatic model.
Automatic Bilge Pumps
Automatic bilge pumps turn on when water reaches a predetermined level. Depending on the design, they use an integrated float switch or electronic water-sensing technology.
The biggest advantage is convenience and protection when nobody is aboard. An automatic pump can remove accumulating water while your boat is sitting at the dock, on a mooring, or stored in the water.
Automatic pumps are particularly useful for boats that remain in the water for extended periods.
Some options available at REDI Marine include:
Rule 360 GPH Standard Bilge Pump Kit with Float Switch
A compact, automatic 12V solution that includes a separate float switch. Features include ignition protection, a stainless-steel shaft, a backflow preventer, and a three-year warranty.
Shop the Rule 360 GPH Automatic Bilge Pump
T-H Marine HYDRA Automatic Bilge Pump – 1100 GPH
For boat owners looking for a higher-capacity automatic pump, the T-H Marine HYDRA features an integrated Sure-Start float switch, anti-airlock design, a 316 stainless-steel motor shaft, and a removable nozzle for easier maintenance.
Shop the T-H Marine HYDRA 1100 GPH Automatic Bilge Pump
Electronic-Sensing Bilge Pumps
Another option is an electronic-sensing bilge pump.
Rather than relying on a conventional float switch, these pumps periodically check for the presence of water by monitoring resistance at the impeller.
For example, the Rule Electronic Sensing Bilge Pump periodically activates to check for water. When water is detected, the pump continues running until the water is removed.
REDI Marine offers two options:
These models eliminate the need for a separate float switch and provide automatic operation.
Manual Bilge Pumps
Non-automatic electric bilge pumps operate when activated by a manual switch or an external automatic switch.
These pumps are commonly used as primary pumps with a separate float switch, as secondary pumps, or in installations where the operator wants direct control over pump operation.
A manual pump can also be a good option when adding a higher-capacity backup pump to an existing automatic system.
3. Consider Your Boat's Size and Intended Use
Not every boat needs the same bilge pump configuration.
A small freshwater fishing boat has different requirements than a 30-foot offshore center console that spends long days running in open water.
Here are some general considerations:
Small Boats, Jon Boats, and Skiffs
Smaller boats often have limited bilge space and relatively modest water-removal requirements.
A 360–500 GPH pump may be appropriate for certain installations, depending on the boat's design and expected water intrusion.
Mid-Sized Boats and Center Consoles
For many recreational boats, a 750–1,100 GPH pump is a useful starting point when evaluating options.
The Rule 800 GPH Electronic Sensing Pump and T-H Marine HYDRA 1100 GPH models are worth considering.
Larger Boats and Offshore Vessels
Larger vessels and boats operating offshore may benefit from higher-capacity pumps and multiple bilge pump installations.
A 1,500–2,000 GPH pump can provide additional pumping capability, although the correct configuration depends on the vessel's design, compartment layout, and applicable requirements.
For example:
Rule 1500 GPH Bilge Pump
A fully submersible 12V pump featuring a 1-1/8-inch discharge outlet, anti-airlock protection, a corrosion-resistant design, and an easy-clean strainer.
Shop the Rule 1500 GPH Bilge Pump
Attwood Heavy-Duty 2000 GPH Bilge Pump
Designed for demanding applications, this 12V pump features a ball-bearing motor design, a 1-1/8-inch outlet, and a three-year warranty.
This is a non-automatic model, so it requires a separate switch or automatic control system.
Shop the Attwood Heavy-Duty 2000 GPH Bilge Pump
4. Don't Overlook Installation Space
A pump can have an impressive GPH rating and still be the wrong choice if it doesn't physically fit in your boat.
Some bilge compartments are extremely tight, particularly around inboard engines, stringers, fuel tanks, and other equipment.
Before purchasing, measure:
- Available mounting height and width.
- Distance between the pump and the bilge floor.
- Discharge hose diameter.
- Available discharge routing.
- Electrical wiring access.
If your boat has a particularly shallow or confined bilge compartment, consider a low-profile pump.
Whale Supersub 1100 GPH Low-Profile Automatic Bilge Pump
The Whale Supersub is designed specifically for narrow and awkward bilge spaces where conventional pumps may not fit.
Its compact design, rotating outlet configuration, and automatic operation make it an interesting option for installations with limited clearance.
Shop the Whale Supersub 1100 GPH Automatic Bilge Pump
5. Should Your Boat Have More Than One Bilge Pump?
For many boats, having multiple bilge pumps is a smart safety decision.
A single pump can fail because of debris, a damaged impeller, electrical problems, a failed float switch, or a blocked discharge hose.
A multiple-pump configuration provides an additional layer of protection.
Depending on the vessel, a typical arrangement might include:
- A primary automatic bilge pump for routine water removal
- A secondary, higher-capacity pump positioned to provide additional pumping capability
- A separate manual pump for emergency water removal.
On larger vessels, separate bilge compartments may require independent pumps.
Remember that adding a second pump does not automatically mean doubling your protection. Both pumps should have appropriate electrical protection, reliable power sources, properly routed discharge hoses, and accessible strainers.
The boat's battery capacity and charging system should also be considered, particularly when automatic pumps are expected to operate while the boat is unattended.
6. Check the Electrical Requirements Before Purchasing
Marine bilge pumps are commonly available in 12V and 24V configurations.
Most recreational boats use 12V electrical systems, while larger vessels may use 24V systems.
Always verify the pump's operating voltage before purchasing.
You should also check:
- Recommended fuse or circuit breaker size.
- Pump amperage.
- Wire guage requirements.
- Total wiring distance.
- Appropriate marine-grade wiring and connections.
- Compatibility with your existing float switch or control panel.
Never assume that a 12V pump can be installed directly into a 24V system.
Proper installation and electrical protection are essential for reliable operation.
7. Keep Your Bilge Pump Maintained
Even the best bilge pump requires periodic inspection.
A pump that worked perfectly last season may not work when you need it most.
Make bilge pump inspection part of your regular boat maintenance routine.
We recommend:
- Remove debris fromthe bilge and pump strainer.
- Inspect the discharge hose for cracks, kinks, and obstructions.
- Check electrical connections for corrosion.
- Test automatic float switches and electronic-sensing functions.
- Verify that water discharges overboard when the pump operates.
- Inspect wiring, fuses, and battery condition.
Also check for backflow from the discharge hose after the pump shuts off. A poorly configured discharge system can allow water to return to the bilge.
A few minutes of preventive maintenance can help prevent an unpleasant surprise at the dock or offshore.
8. Which Bilge Pump Should You Choose?
If you're still trying to decide which pump is right for your boat, here's a quick summary of some options available at REDI Marine:
- Compact automatic installation: Rule 360 GPH with Float Switch.
- Automatic electronic sensing: Rule 800 GPH or 1100 GPH Electronic Sensing.
- Higher-capacity automatic pump: T-H Marine HYDRA 1100 GPH
- Higher-capacity manual pump: Rule 1500 GPH.
- Tight installation spaces: Whale Supersub 1100 GPH Low Profile.
- Heavy-duty 2000 GPH application: Attwood Heavy-Duty 2000 GPH
The right choice ultimately depends on your boat's layout, electrical system, water intrusion risk, and required pumping capacity.
Find the Right Marine Bilge Pump at REDI Marine
Choosing the right bilge pump is about more than simply selecting the highest GPH rating. It's about matching the pump to your vessel, ensuring proper installation, and having a reliable system that works when you need it.
At REDI Marine, we offer a selection of marine bilge pumps from trusted manufacturers, including Rule, Attwood, T-H Marine, and Whale.
Whether you're replacing an existing pump, upgrading to a higher-capacity model, or adding an automatic backup system, we're here to help you find the right equipment.
Shop our complete selection of marine bilge pumps:
https://redimarine.com/search?q=bilge+pump
REDI Marine – Quality Marine Equipment for Your Next Adventure.