Automatic Float Switch

Add an Automatic Float Switch

by Conrad & Judy Kreuter

Some bilge pumps come equipped with an internal automatic float switch. If your bilge pump does not have a float switch, adding one is a very good idea.

A float switch measures the water level in the bilge and activates the bilge pump when the water level becomes too high. All bilge pumps can be retrofitted with an automatic float switch. These switches should be wired directly to the battery positive terminal so that they operate even when the boat is not in use.

Consult your marine parts dealer to select the correct automatic float switch for your application. He will also be able to supply the necessary fuse holders, fuses, terminals and wire required to complete the installation.

To install the float switch, locate the lowest part of the bilge and orientate the switch in the fore and aft direction. Some boats have a built in pad for mounting the pump and switch with small self-tapping screws. If your boat does not have this pad, you may want to use epoxy glue to hold the switch down.

Locate the brown wire coming from the bilge pump and cut it about 18” from the pump. Connect and crimp one of the wires from the auto float switch to one of the cut brown wires in one end of a waterproof butt splice connector. Slide the remaining brown wire to the other end of the butt splice connector and crimp. Attach the remaining wire from the float switch to one end of a waterproof fuse holder and the other end of the fuse holder attaches to the battery positive terminal. Install a 7.5 amp fuse in the fuse holder. To test the installation, simply lift up on the float switch and the pump should run. You can also turn on the bilge pump from dashboard switch.

If the float switch does not come with a cover to keep debris from getting stuck under the switch arm, purchase the appropriate part from your marine parts dealer.