How to Install a Bilge Pump Float Switch

A bilge pump float switch turns the bilge pump on automatically when the water passes a certain level in the boat. Here are a few instructions on how to install a bilge pump float switch.

Tools and Materials

  • 3-way switch
  • Tape

Step 1: Purchasing the Right Bilge Pump Float Switch

When you buy your bilge pump float switch be sure that it is compatible with the bilge pump on your boat. A lot of bilge pumps will run on a 12V DC power and it is very important that your float switch is intended for the use of 12V power. Also be certain that the switch is rated slightly higher than the bilge pump's wattage draw. Make sure that your float switch has wires long enough that it can be connected with the bilge pump and pump control switch.

Step 2: Getting the Battery Ready

Disconnect the wire that is on the negative battery terminal. This is to avoid the chance of electrocution.

Step 3: Positioning the Bilge Pump Float Switch

The position of the float switch is close to bilge pump. The float switch should be sitting equal with the bilge pump or slightly higher. The float switch sits in this position so that the bilge pump isn't activated until the water level reaches the pump.

Step 4: Mounting the Bilge Pump Float Switch

Mount your bilge pump float switch to the hull of the boat using the instructions that came with the float switch. There are many mounting methods used, as they vary according to the different models. When you are working on your hull you always have to be cautious.

Step 5: Running the Wires

The wiring of the switch has to run to the manual bilge pump control switch. When you are running the wires, try using an area that is out the way. Many people choose to run the wire through the bilge. Nonetheless, if you do it this way be sure to avoid running the wire where it will be continuously wet.

Step 6: Connecting the Wires to the 3-Way Switch

The 3-way switch will replace the manual bilge pump switch. The powered wire from the manual switch is connected with the line terminal of the 3-way switch. Connect the bilge pump wire to the switched terminals of the 3-way switch. Now connect the float switch by connecting a wire to each switched terminal on the 3-way switch.

Step 7: Checking that the Bilge Pump Float Switch Works

First, connect the negative cable back onto the battery. Flick the switch on the 3-way switch to off. You shouldn't hear anything from the bilge pump. Position the switch to automatic and again the bilge pump should be off. The bilge pump should start working when the switch is in the manual position. Flip the 3-way switch to automatic again and fill the bilge with some water. As soon as the water level is passed, the float switch and the bilge pump should start to empty the water from the bilge. You now have completed the installation of the bilge pump float switch.