Last Updated on March 01, 2020
Biltges have been integral to boat design for centuries, and are believed to have originated with the ancient Greek trireme warships. A bilge is a space or tank below the water line between the lower deck and the outer hull.
They serve the important function of collecting all the rainwater, sea water, and other liquids that would otherwise end up sloshing around on deck if there were no drains to draw them down to the bilges. During the Age of Sail, bilge water was often pumped out by hand and used to fight shipboard fires in an emergency. Today, bilge water is simply contained until the bilge tank or space becomes full, at which point they are emptied into the water via an automatic motorized bilge pump.
Since the inclusion of bilges on ships and boats, bilge pumps have evolved to keep pace with advances in technology. Originally made of wood or bronze, bilges are now constructed from plastic and are run by electric motors rather than by hand. To help you make sure you install or replace your automatic bilge pump with the right automatic bilge pump, we’ve assembled this reviews and buyers’ guide. Check out what we have for you.
Selecting the Best Automatic Bilge Pump in March, 2020
1. Rule 25S-Marine
12 Volt /24 Volt
2. Seaflo Automatic Submersible Boat Bilge
3. Amarine-made Automatic Boat Bilge
4. Sahara Automatic Boat Bilge
5. Rule-Mate Automatic Bilge Pump
12 Volt /24 Volt
Why Do I Need an Automatic Bilge Pump?
Trust me, checking your bilge tank and pumping it out the old fashioned way is difficult, sweaty work. Automatic bilge pumps can be installed with minimal effort, and they will ensure your bilge tank or tanks are emptied automatically as soon as they reach a certain level. So long as you check your automatic pump periodically to make sure it stays clear of debris and buildup, you should rarely have to concern yourself about it.
That being said, having the right one can make all the difference in your boat maintenance schedule, too. It’s like any seemingly minor component on a boat or ship: you never realize how important it was until it breaks.
Recommended Automatic Bilge Pumps
1. Rule 25S-Marine 500 Automatic Marine Bilge Pump
An excellent choice for smaller watercraft, the Rule 25S-Marine 500 Automatic Bilge Pump is easy to install and maintain. Rather than using an internal or external float switch, this centrifugal bilge pump measures water pressure against the impellers to determine whether it needs to activate. It does create a draw on your electrical system as it periodically checks the bilge level, but you also don’t have to worry about the sensor wearing out anytime soon either.
2. Seaflo Automatic Submersible Automatic Bilge Pump 12v 750gph - (Editor’s Choice)
Suitable for longer power boats that have shallower bilges, this submersible unit from Seaflo keeps your bilges emptying automatically with an impressive 750 GPH output. The pump’s mechanism is a centrifugal impeller, and it is float activated to eliminate power use when the pump is not in operation. Best of all, it is virtually silent and vibrationless, cutting down on noise when you may be fishing or taking in the night sky.
3. Amarine-made Automatic Submersible Boat Bilge
Looking for an inexpensive replacement automatic pump? Amarin-made has you covered with this compact-yet-powerful 750 GPH float-switch activated automatic bilge pump. A centrifugal impeller pump with an impressive power output, this bilge pump minimizes power usage thanks to its use of an integrated float switch that activates and deactivates the pump for the current water level.
The housing and motor are both ruggedized for extended wear and use, and it is suitable for both saltwater and freshwater use. If you have a small to medium sized powerboat, this little centrifugal pump has you covered.
4. Sahara Automatic Boat Bilge Water Pump
As complete automatic bilge pump replacement kits go, nobody builds them like Sahara. Every required replacement or installation component is included in the box and built to the most exacting standards. The included wiring kit is caulked to prevent anything from damaging the insulation even after years of use submerged in saltwater, and the permanent magnet motor features a stainless steel shaft with steel-reinforced seal to protect it against the elements for years to come.
Activation is water pressure-based, and the mechanism is a centrifugal impeller, both of which make this an ideal option for shallow bilge powerboats. If you want a replacement or upgrade bilge pump kit with everything in one box, this is the one to buy.
5. Rule-Mate Automatic Bilge Pump, No Float Switch Required, Water Sensing
This pump only draws current when the bilge needs pumping out, and it has zero draw when not in operation thanks to its passive sensor system. Best of all, the impeller is designed to reduce potential fouling, and the filter can be quickly removed and reattached for fast cleaning as needed. As centrifugal bilge pumps go, this is definitely the cream of the crop.
Things To Consider When Choosing an Automatic Bilge Pump
Here are the features to check out before buying an automatic bilge pump.
Type of Boat
Daysailers and open skiffs with outboard motors are fine with a piston manual pump, a hand bailer, or a good old fashioned bucket. Runabouts and ski boats generally need at least one electric bilge pump towards the stern or at the lowest point in the bilge itself. Small cruisers and racers generally have a large manual pump mounted in the cockpit since they need to be emptied less frequently.
If you have a racing sailboat, you are required by international law to have two manual pumps. One must be operable from the cockpit, and the other from below decks. Finally, coastal and offshore boats need electric bilges for each bilge compartment that holds water, and a large manual pump should also be kept on board for emergencies or in the event of a power failure.
Size of Your Boat
Different automatic pumps work best for different boats. Power boats 18 feet and are usually fine with a 300-500 gallons per hour (GPH), but anything over that to 23 feet usually requires a 450-700 GPH output. If you’ve got an even bigger boat (up to 26 feet), you are looking for a pump in the 700-1100 GPH range.
Sail boats, like large powerboats, also need a bilge for each compartment that can hold water, as well as a manual backup for each. To give you a ballpark GPH flow rate to look for, a 600-800 GPH pump is sufficient for up to a 26 foot boat, while a 40-45 foot boat needs up to a 4,000 GPH pump.
Large power boats need more powerful bilge pumps than sailboats, as they have a shallower draft and bilge area that needs to be emptied more frequently. An 800-1200 GPH pump is good for up to a 30 foot power boat, and a 40-45 foot vessel needs up to a 4000 GPH capacity bilge pump. Manual backups are required by law, but you don’t want to have to manually pump out bilges this big.
If your boat has an existing electrical system, you want to wire up an automatic bilge pump. Manual pumps are certainly effective, but they require almost as much effort as hand balers and buckets.
Even if you have just a smaller power boat or runabout, you’re always better off with an automatic bilge pump backed up by a manual system. Boating with a manual bilge pump can take all the joy out of your time on the water, so do yourself a favor and install an automatic pump. Your friends, family and your arms and back will thank you for it.
Automatic Switch Type
There are three types of switches for automatic bilge pumps, and some are better suited to specific types of boats and how you use them.
Separate Float Auto-Switches
One of the more popular automatic bilge pump switching systems, a separate float switch uses a hinged arm switch attached to a bobber. When the water level in the bilge gets high enough, the float forces the switch arm up to activate the pump system. When the water level in the bilge area drops to a low enough point, the arm sinks back down with the float switch and deactivates the system. This is a popular design or conversion for older manual electric bilge pumps, but it does have a few drawbacks we’ll discuss later.
Another float based system typical of most replacement and upgrade automatic bilge pumps, these models have a built-in float. Thanks to the integral nature of the float switch though, these pumps are more effective in tighter vertical spaces than separate float auto-switch models. Some also use an internal electronic timer to run the motor every so often to detect if there is water in the bilge that needs to be pumped out. Like the separate auto-float systems, integral auto-switches also have their drawbacks, but we’ll talk about that in the product reviews.
Water-sensing Electronic Auto-Switches
The ideal automatic switching system for bilge pumps, water-sensing electronic auto-switches check the water level via their integrated detector cells. These cells use a low-impedance electrical field do determine if the bilge is full or close to full and needs pumping.
What makes this system the best is they do not use moving parts that can wear out, and they don’t activate if they detect petroleum products in the bilge. This last feature is extremely important should you spill fuel on deck and it drains into the bilge. It’s by no means a perfect switching system, but it’s as close as you can get to perfect in some models.
Centrifugal Pumps vs. Diaphragm Pumps
How the water is pumped out by your automatic bilge pump determines both its effectiveness and expected lifespan. Centrifugal pumps are both non self-priming and can only function when submerged. They are best installed in bilges with smaller sumps, and they use internal rotating vanes to move fluid to the center of their sphere before extruding it via their outlet port. Most also come preinstalled with a mesh filter on the intake to prevent debris from fouling the vanes on the internal impeller, too.
Diaphragm pumps are all self-priming, so they can easily pull water through their intake hose before expelling it into open water. Water is shifted through the pump via a flexible membrane that expands and contracts inside the pumping chamber, drawing bilge water in before pushing it through the pump exhaust valve. As with the centrifugal pump, you need a strainer on the intake hose to prevent debris and sludge in the bilge from clogging up the pumping chamber and jamming the pump.
Automatic Bilge Pump Buyers Guide
Here’s a summary of what to look for in your automatic bilge pump when you are shopping around:
Does your bilge pump move water at a fast enough GPH to clear your bilges as they fill up? Getting an insufficiently powered pump means you run the risk of destroying the pump’s motor due to overworking it, and when the motor fails it has the potential to damage your electrical system as well. Make sure you follow the above listed guidelines for flow rate versus boat size.
Does your existing electrical system have enough amperage to run the bilge pump you need? If it doesn’t, you can potentially cause expensive damage that will require you to replace wiring, batteries, generators and even engine alternators. Make sure you account for your bilge pumps amperage needs when calculating how much power the boat needs to run all its onboard systems.
Centrifugal pumps are generally not a great fit for sailboats and boats with deeper keels and bilges since they need to be submerged and thus require longer hoses to pump the water up and out. Diaphragm pumps are best for deep keeled vessels since they can draw water up an intake hose without needing to be submerged.
In larger boats, you are required to install a bilge pump for every compartment that can hold water. Ensuring you place the correct type of bilge pump in each compartment in the right place to properly empty the bilges is critical to safety, especially on larger ocean-going boats. You also need to evaluate your electrical system and how you will power your bilge pumps if you are upgrading manual pumps to automatic pumps.
Hoses and Fittings
Each pump will have specific manufacturer specifications about how and where it can be installed, as well as what type of hose and specific gauge of wire is needed to ensure reliable operation. DO NOT deviate from the recommended manufacturer installation specs, as you risk causing expensive damage to your boat’s hull and the electrical system. Poor hose fittings and mountings can also increase the potential for leaks or pump failure, so make sure you fit it correctly the first time and fit it well.
What size wire do you need to power your automatic bilge pump?
The gauge of the wire you use is determined by the flow rate of the pump and its amperage draw. Here’s a quick rundown of flow rates and wire gauges:
- 800 GPH = 16 GA
- 800-2000 = 14 GA
- 2000-3500 = 12 GA
- 4000= 10 GA
What are some common causes of bilge pump failure?
-Flow restriction in diaphragm pumps can burn your motor out when the pump is no longer able to expand or contract. Centrifugal pumps are less likely to burn out the motor, but that doesn’t mean they can’t get jammed up by flow restriction in the absence water flow.
-Siphoning can occur if the bilge exhaust port is not above the water line, causing outside water to flow backward through the pump and into the bilges. This is why all outward ports on bilge pumps are placed well above the water line.
-Clogged intake filters can cause pumps to stop working if enough debris and grime builds up on them to prevent water from getting through. There’s also potential for tiny debris to pass through the filter and accumulate on the impellers or diaphragm of your pump, reducing the volume of the pumping chamber and reducing output capacity.
-Bad Wiring/dead batteries are a common cause of failure on seagoing boats. Fuel contamination, cleaning agents, and saltwater are hard on wiring insulation, and can cause wiring and battery contacts to corrode and short out over time. Using waterproof heat shrink on all connections helps prevent this from occurring.
Why get an automatic bilge pump instead of a manually activated pump?
A manually operated electric or manual piston bilge pump may be fine if you typically stick to lakes, rivers and other relatively calm water. When boating in rough weather, you don’t want to worry about bailing water out of your boat in a storm or checking to see if the bilge needs to be emptied.
A manually operated piston pump or a manual switch electric bilge pump will get you by in a pinch, but if you forget to turn them on you may start foundering or even sinking if you don’t hit the switch or start pumping in time. An automatic electric bilge pump is always going to be the best choice for safer boating.
What are the best brands for automatic bilge pumps?
Every part has its OEM copies and knockoffs, and many of them work nearly as well as the manufacturers covered by our reviews. However, the top names for automatic electric bilge pumps are as follows:
What performance can I expect compared to a manual switch or manually operated bilge pump?
The primary advantage in performance is you don’t have to constantly check your bilge level, or run/operate your bilge pump with the risk of running it dry and burning out the motor. You should always have manual switch backup or hand-powered piston pump for safety, but an automatic pump is always going to offer you far more performance keeping your bilge level under control for significantly less effort.
What disadvantages are there to installing an electric auto-switching bilge pump?
The only drawbacks you need to concern yourself with are the maintenance schedule and the installation requirements. Running power lines for the pump may require some experience with electrical work, and you need to make certain that your wiring is properly insulated against both seawater and freshwater exposure. Sealing your wiring work with caulking is also important.
As for regular maintenance of your pump, you need to make sure that you are clearing your intake filters before heading out on the water each time. Otherwise, you may end up with a blocked intake, your pump will run dry, and the motor will be ruined. About once a year, you need to have your bilge flushed out to prevent accumulation of debris and residue. Both are small enough to bypass your intake filter, and they can accumulate on the impeller or in the diaphragm chamber of your automatic bilge pump, eventually causing it to burn out. So long as you do a solid job on the installation and keep your bilge and intake filters clean, you should have no issues.
Get the Seaflo Automatic Submersible Boat Bilge. It’s the best value for the money, it works exceptionally well, and the low-impedance field sensor is virtually foolproof. Unless you install it incorrectly, this little centrifugal automatic bilge pump will give you years of excellent service with minimal maintenance and hassles.