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How to install a fuel tank gauge on a boat

Updated July 20, 2017

When you're out on a boat, you may need to know how much fuel you have left without looking inside the tank. An electrical fuel gauge can help you. Electrical gauges are used when the tank is internal and some distance from where you operate the boat. A fuel sender attached to the tank sends a signal through a wire to the fuel gauge, which is mounted in your instrument panel.

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  1. Mark the centre point where the gauge is to be installed on your instrument panel. With the aid of a hammer, make a notch in the panel.

  2. Attach a hole cutter with a cutting diameter the size of the gauge to a drill. Rest the centre tip of the hole cutter in the notch, preventing the hole cutter from sliding away from where you want the hole to be. Cut a hole in the panel.

  3. Insert the gauge in the hole so it rests against the flange on the face of the panel. Using the bracket that comes with the gauge, attach the gauge. Line up the two holes in the bracket with the longer studs on the back of the gauge. Screw the nuts on the studs, allowing the bracket to secure the gauge in place.

  4. Insert a measuring tape through the mounting hole, located on the top of the fuel tank. Measure the distance from the bottom of the tank to the outside top of the tank.

  5. Loosen the adjustment screw on the float arm that is attached to the sending unit below the mounting plate. With the measuring tape, adjust the length of the float arm until it is 6 mm (1/4 inch) below the tank measurement. Tighten the adjustment screw.

  6. Loosen the set screw on the arm of the float and insert the fuel sender into the hole on the top of the tank. Adjust the arm until the float just comes in contact with the bottom of the tank. Tighten the set screw. Line up the holes on the tank with those on the sender base, making sure the rubber gasket is between the tank and the base plate. Secure it using screws.

  7. Slide a rubber gasket over the float and float arm, and align the holes in it with the holes in the mounting plate. Lower the float and float arm into the tank, making sure they are at a distance from the nearest tank walls to prevent the arm movement from being obstructed.

  8. Align the mounting holes in the tank with those in the mounting plate. Place a small amount of rubber sealant over the holes and install the mounting screws.

  9. Measure and cut a length of the pink and black wire from the rolls to reach from the electric fuel sender to the back of the electric fuel gauge. Always add some extra length to account for bends required during routing.

  10. Bare the two wire ends at the fuel sender using a wire stripper. Crimp a ring terminal on the pink wire and a fasson terminal on the black wire. Slide the fasson terminal on the ground terminal fastened to the mounting plate. Place the ring terminal over the centre post of the mounting plate and secure with the accompanying nut, using the adjustable spanner.

  11. Locate the common ground post at the back of the instrument panel; it will have several black wires going to it from the other instruments. Bare the two wires coming from the fuel sender and crimp on the ring terminals. Attach the black wire terminal to the common ground post, and the pink wire to the terminal marked SENDER at the back of the fuel gauge.

  12. Cut a short piece of black wire from the roll. Bare the ends and crimp a ring terminal on each end. Attach one end to the terminal on the fuel gauge marked ground (GRND) and the other end to the common ground post.

  13. Measure a length of the white wire to run from the ignition switch to the fuel gauge.

  14. Bare the ends and crimp on ring terminals. Attach one end to the terminal on the back of the fuel gauge marked ignition (IGN).

  15. Disconnect the ground terminal from the battery. Attach the other end of the white wire to the terminal marked IGN on the ignition switch. Reconnect the ground terminal to the battery.

  16. Tip

    There is a lamp in the electric fuel gauge to provide back lighting. In some cases these are prewired in the gauge itself. If not, there will be one black and one white wire coming from the back of the fuel gauge. Bare the ends of the wires and attach ring terminals. Attach the black one onto the GRND terminal on the back of the gauge with the black wire attached earlier. Attach the white wire to IGN on the back of the gauge, sharing the terminal with the previous white wire.


    Caution should be taken when working in the back of an instrument panel to avoid interrupting wiring going to other instruments. Take extreme caution if the tank has or has had fuel in it as the vapours are highly volatile. No smoking or open flame while working around a fuel tank.

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Things You'll Need

  • Fuel gauge
  • Electric fuel sender
  • Black, pink and white rolls of wire
  • Ring terminals
  • Female fasson terminal
  • Wire crimping tool
  • Wire stripper
  • Screwdriver
  • Adjustable spanner
  • Hole cutter
  • Electric drill
  • Hammer
  • Center punch
  • Rubber sealant

About the Author

Living in Nanaimo, British Columbia, Len Engst has been writing articles on chemistry and electronics since 1966. His earliest publications were in "Defense R&D Canada." He holds a diploma in chemical technology from the Northern Alberta Institute of Technology in Edmonton and a diploma in electronics from ICS Toronto.

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