How to Install a Trim Switch in a Boat

How to Install a Trim Switch in a Boat

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A boat's trim switch activates the trim/tilt system that raises and lowers your outboard motor. The switch has three positions, for "Up," "Down" and "Off." The center terminals direct or disconnect the electrical power, one set of terminals sends the power to the "Up" side of the trim/tilt system and one set sends the power to the "Down" side. The center position is "Off."

Items you will need

  • 3-position switch

  • Soldering gun

  • Silver-bearing rosin-core solder

  • Stranded copper wire, red insulation

  • Stranded copper wire, black insulation

  • Wire stripper

  • Screwdriver

  • Spray vinyl insulation

Step 1

Locate the "Up" wires for the trim/tilt system. Consult the motor operator's guide to find out which of the wires leading from the trim/tilt system's hydraulic pump are the "Up" wires and which wires are the "Down" wires.

Step 2

Connect the "Up" wires to the two posts on one of the ends of the three-position switch. If you solder the wires to the switch's terminals with a soldering gun, use silver-bearing rosin-core solder for the connection.

Step 3

Connect the "Down" wires to the two posts on the opposite end of the three-position switch from the "Up" wires.

Step 4

Strip the ends of two lengths of stranded copper wire, one with red insulation and the other with black, with a wire stripper. Attach the red length of wire to one of the center terminals of the three-position switch. Attach the black length of wire to the remaining center terminal of the switch.

Step 5

Loosen one of the screws on your boat's common power bus, located under your boat's dash, with a screwdriver. Wrap the red power wire from the center terminal of the switch clockwise around the screw and tighten the screw. Connect the black wire from the switch to the boat's common ground.


  • After you've made the electrical connections, spray a coat of a spray vinyl insulation over the connections to help make them water resistant.
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