How to Install an Automatic Bilge Pump on a Boat

Written by chris stevenson
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How to Install an Automatic Bilge Pump on a Boat
The automatic bilge pump is an essential and practical safety device for any boat. (boats image by pearlguy from

Recreational boating requires numerous safety factors that must be taken into consideration before any trip or outing. One of the most essential items on-board any watercraft is a bilge pump, whether a manual model or an electric automatic version. Boaters must have a system to remove excess water from their bilge (sump) area. With excess water comes excess weight that affects boat handling characteristics and safety factors, least of which might include sinking. Automatic bilge pumps can remove dangerous water levels in the bilge area, and should be considered a priority installation for any small watercraft.

Skill level:

Things you need

  • Socket set and wrench
  • End wrenches
  • Screwdrivers (Phillips and slot)
  • Drill motor and bits
  • Hole-saw bit
  • Bilge pump kit (automatic)
  • Wire (8- or 10-gauge)
  • Wire clamps and ties
  • Heat shrink tube
  • Silicon (waterproof)
  • Rubber hose (smooth bore)
  • Float switch (if not provided)
  • Wire crimps (butt connectors)

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  1. 1

    Make sure the bilge (sump) has been evacuated of all water---dry it thoroughly. Disconnect the negative battery cable. Position the pump in the lowest part of the sump area for installation of the submersible type pump. Whether you have a complete pump kit with all of the fastening hardware or purchase individual pieces, you must fasten the pump down to the hull using two options: drill holes in a nearby stringer and bracket the pump to it, or use waterproof epoxy glue to glue the bolt heads down, allowing the threads to point upward so you can align them with the pump-mounting bracket and fasten the nuts.

    Fasten the float switch mechanism in the same manner---low in the sump and unimpeded by other components, wires or hoses.

  2. 2

    Use the drill motor and a hole saw to drill a discharge hole through the transom or side of the hull, well above the waterline. Make the hole larger than the discharge hose diameter. Install the grommet and discharge nozzle inside the hole, using the kit parts. Measure out a length of smoothbore hose that leads from the pump outlet to the discharge hole. Leave plenty of hose for routing purposes. Keep this distance as short as possible, making no sharp bends. Secure one end of the hose to the pump outlet with a hose clamp (or kit fastener).

  3. 3

    Rout the hose toward the pump discharge nozzle, starting at the pump, and secure it to the runners or hull with the brackets. Use a bracket about every 18 inches, or use a tie strap to secure it to a part of the boat structure. Secure the end of the hose to the discharge nozzle, using a hose clamp and a screwdriver. Use the screw-on hose fasteners if they came with the kit.

  4. 4

    Connect a red positive wire (kit wire or your own) to the positive lead on the pump connector. Use shrink wrap around this connection if you wish, for extra protection. Run the positive wire to the positive side of the float switch connection and fasten it. Run another red wire from the positive float switch connector post up to the positive battery terminal. Route this wire as you go, securing it to the small brackets provided, or use tie straps to secure it. Before you fasten the wire to the positive battery terminal, splice in a small in-line fuse about 12 inches from the positive battery terminal. Use the male and female snap connectors to join the fuse ends to each end of the wire. Use an eyelet fitting to connect the wire to the positive battery's crimp bolt.

  5. 5

    Cut a length of black wire with enough excess to allow for routing from the negative pump terminal to the float switch (negative side), and then to the negative battery side. Route and secure the wire as you did with the positive wire, only tie-strap the negative wire to the positive wire. Secure the black wire to the battery's crimp bolt by using an eyelet fitting.

  6. 6

    Reconnect the negative battery terminal. Test the pump operation by gently lifting the float switch lever to the up position. The pump should activate.

Tips and warnings

  • When securing screws into the boat structure, use a dab of waterproof silicone on the end of the screw.
  • Install a three-way switch if you prefer operating options for your pump. The three-way switch has an "on," "off" and "automatic" selector switch. Install it according to the direction diagram that comes with the kit.
  • Use shrink wrap around all electrical connectors once they are secure.

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