How to Test a Bilge Pump
No matter what boat you're on, the bilge pump is likely going to be in the lowest, nastiest part of the boat because its job is to pump out the most amount of water that comes aboard.
Obviously you want the bilge pump, its float switch and all of its electrical components and connections to function, as they all work together to remove nuisance water and help keep the boat afloat. Watch the video above or read on below for several ways to test bilge pumps.
NOTE: The easiest way to test bilge pumps is to remove them from the boat. Also, bilge pump systems vary, so some of the details below may not apply to all bilge pumps.
Tools Needed - Bilge Pump Testing
The first set of testing involves a battery, a three-way switch, an external float switch, and the bilge pump itself, with the pump and the float switch connected to the three-way switch, which is connected to a battery. With this configuration, you lift up on the float switch and it activates when the three-way switch is in the run position. When the three-way switch is in the middle position, lifting the float switch doesn’t do anything, but in the momentary position you can manually activate it.
Testing a Standard Bilge Pump
Step 1. Check for battery power, and make sure the fuse is of the correct ampacity and that it’s not blown. Use a test light on the load side of the fuse to see if it lights up. Next, check the battery side of the fuse, which goes through the filament and then out to the load side. If both sides light up the test light, the fuse is good.
Step 2. Put a test light to each of the terminals of the three-way switch to see if they work. Test the input, the momentary output and the on position output next to it by pushing the button for each one with the test light attached. If all three activate the test light individually, the three-way switch is working.
Step 3. Remove the fuse so you can test the resistance values going back and through both the bilge pump and the switch itself.
Step 4. Check to see if the wiring is complete and available to send power through the bilge pump by using the leads of a multimeter (set to resistance testing) between the black and green wires on the three-way switch (disconnected). The resistance reading should be under 1 ohm.
NOTE: The resistance should be under 1 ohm, since the flat resistance of the three-way switch is 0.2. The flat resistance is found by putting the negative and positive leads of the multimeter together, so the 0.5 ohms is within range.
Step 5. Set the multimeter to sound verification (audio test) to check the continuity with the float switch is working by putting the leads of the multimeter between the white and green wires on the three-way switch. Lift the float switch up and listen for a beep, which means it’s working.
NOTE: We worked with a completely sealed wiring system, where everything is heat shrunk and watertight. When testing the wires, be careful poking into them while testing to avoid making holes that would allow water to destroy the wiring.
The next testing phase involves an automatic bilge pump with an internal float switch and a regular on/off two-way switch attached to a battery. This type of bilge pump system is hardwired going through the switch back to the pump to where you can’t shut it off, which is great for people who forget to run their bilge pumps.
Automatic Bilge Pump Test
Step 1. Make sure that the fuse is of the correct ampacity, and use the test light on the load side of the fuse to check if it lights up.
Step 2. Test that the two-way switch is working by turning on manual mode and touching the manual side with the test light to make sure power is coming in. The test light will illuminate and the pump will turn on if it’s working.
Step 3. Check the wires for the motor by first removing the fuse, then measuring from the negative side back to the manual side of the motor itself on the two-way switch. In this case it’s the white wire to the negative. The multimeter should read less than 1 ohm to indicate it’s working.
NOTE: We got a 0.5. reading, which means the motor is working.
Step 4. Test the internal switch by first reinstalling the fuse, then turning the two-way switch on manually and listening for the pump’s motor to run. Next, turn off the two-way switch and check for a test dot on the back of the bilge pump. Put your finger on the test dot and hold it for five seconds, and listen for the motor to run.
NOTE: This testing feature on the Rule-Mate pump we tested may not be available on all automatic bilge pumps.
Step 5. Run an internal float switch test by filling a bucket or other container with water and submerging the bilge pump in it. Wait at least two seconds for the bilge pump to activate, and then another 4 seconds for the pump to start pumping out water.
If the bilge pump doesn’t immediately start pumping out water after being submerged for a few seconds, the internal float switch is damaged and needs to be replaced.
