Bilge Pump Wiring Tips

Wiring a bilge pump doesn’t necessarily require hiring a marine mechanic to do it for you. With the right quality equipment and materials, you should be able to wire your bilge pump yourself and do just fine.

How to wire a bilge pump tips

Basic electrical installation skills should cut it, but keep in mind the wiring will be exposed to damp conditions, especially the section within the bilge compartment, so you’ll want watertight connections. Here are some tips for wiring bilge pumps.

Use Marine-Grade Wire of the Correct Gauge

Use multi-strand marine-grade wire that has the strength and flexibility necessary for use in the bilge pump system. Never use solid, single-strand wire, which is prone to shearing from the constant movement and vibration of a boat.

Ancor marine grade wiring

Ancor multi-strand marine grade wiring

The wire needs to be the right gauge for how many amps your bilge pump draws and the length of the wiring circuit from battery to pump. If the manufacturer specifies a particular gauge wire, follow the guidelines. And if your bilge pump doesn’t have wire gauge specs, contact the manufacturer directly or find a wire sizing chart online. 

Use Marine-Grade Connectors

The wiring system connectors also need to be marine-grade. Use step-down crimp-on butt connectors protected by adhesive-lined, heat-shrink tubing. Don’t wrap them in electrical tape because the tape will lose its adhesive properties and peel off. Add a second layer of heat-shrink tubing over connectors to be doubly sure the connections are absolutely waterproof. 

PICO butt connectors

PICO wiring butt connectors

Wire the Bilge Pump Direct to the Battery

The bilge pump needs to run when the boat is unattended and the power shut off. Wire the pump directly to the battery and not the electrical distribution panel. Next, install an inline fuse, which should be on the wire running from the positive battery terminal, as close to the battery as possible.

Bilge pump wiring marine battery

Add a Float Switch

If the bilge pump doesn’t have a built-in sensor, add a float switch to the wiring circuit. A float switch automatically turns the pump on when it senses water in the bilge, and off again when it senses the water has been removed.

Rule bilge pump float switch

Whale bilge pump float switch

Run Wires Out of the Bilge

Mount the bilge pump at the lowest part of the bilge, where water accumulates and conditions are damp. The bilge pump and float switch’s wiring should run upward and out of the bilge. Fasten the wires with cable ties at regular intervals so there are no slack wires hanging into any bilge water. For additional wiring protection, run them inside a hose or add an extra layer of heat shrink tubing.

Install a Bilge Pump Switch

If you’re installing a bilge pump system from scratch, you’ll need to include a bilge pump switch. If you already have a two-way switch, consider upgrading to a three-way switch. A three-way switch can set the pump to on, off or automatic, running only when necessary.

Sea Dog bilge pump switch

Sea Dog three-way bilge pump switch

Test the Bilge Pump System

Run tests on the bilge pump system before taking your boat out on the water. First, test the float switch by running a hosepipe into the bilge and filling the bilge with water until the float switch turns the pump on. Turn off the water and check that the float switch turns off the pump once the water has left the bilge. Next, test the bilge pump switch by filling the bilge with water again and checking the pump turns on and off as the switch commands.

Bilge pump wiring tips testing

Regularly Check the Bilge Pump System

Bilge pump systems require regular inspection. Test the pump every time before setting out on the water. Inspect the bilge for debris that might block the pump or float switch, and check that the wiring and the connectors are in good shape.

Get a Two-Pump Bilge System

A low capacity bilge pump is good for keeping the bilge free of nuisance water, but inadequate for an emergency flooding situation. Installing a two-pump bilge system consisting of a low capacity pump and a high capacity pump is highly recommended.

Boat bilge pump system

Mount the low capacity pump at the bottom of the bilge to deal with nuisance water, and the high capacity pump higher up in the boat to deal with large quantities of water to prevent flooding. 



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