How to Wire a 12V Boat Switch

Updated April 17, 2017

Your boat has a variety of electrical devices on board, many of which need to be switched on or off manually depending on your moment-to-moment needs. You can install additional 12-volt switches as necessary to accommodate new equipment. Proper installation of the switch will ensure your device operates as designed, without creating a safety hazard.

Locate a 12-volt power source, the grounding block, and the electrical component to be controlled.

Select a convenient location for the switch. This might be near the component to be controlled, near a power source or in a central location like the helm.

Drill pilot holes for the faceplate mounting screws and a larger hole, if needed, for the switch and any routing wires to fit into.

Measure the distance from the switch to the power source, from the switch to the electrical component, and from the component to a grounding block.

Determine the appropriate wire size and cut to length. Marine applications should use at least 14 gauge wire for light loads and heavier gauges for heavier loads and longer runs.

Attach ring terminals to one end of each of the three lengths of wire.

Route the wires to their end locations and install with mounting clips or hangers.

Attach ring terminals to the other end of the wires when you are certain the length is correct.

Connect the positive lead -- the wire that will carry the current from the power source to the switch -- to one side of the switch and to the power source. If the power source is not fused connect an in-line fuse between the power source and the wire lead.

Connect the wire that will carry current to the component to the other side of the switch and the positive connection of the component.

Connect the return wire to the negative side of the component and the grounding block.


Boat cable is available in 2-conductor form and is well suited for marine applications.


Use the correct gauge wire. Using a lesser gauge (thinner) wire can create a fire hazard. Avoid running the wires too close to sources of extreme heat or sharp objects that could damage the wire insulation.

Things You'll Need

  • 12-volt marine grade 2-pole (on-off) switch
  • Drill and drill bits
  • Insulated stranded wire graded for marine use
  • Ring terminal kit
  • Wire mounting clips or hangers
  • Crimping pliers
  • Wire cutter
  • Wire stripper
  • Screwdriver
  • In-line fuse, if required
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About the Author

Steve Hayward is based in Phoenix, Ariz. and has been writing business, technical and how-to articles and manuals since 1992. He has written training guides for major US companies and has published a cookbook. Hayward holds a Master of Arts degree in psychology from the University of New Mexico.