Wiring your boat's navigation lights doesn't need to be a wiring nightmare. Marine safety duplex cable combines the "hot" power wire and the ground wire in a single cable, allowing you to make the run from battery to all the running lights without a cumbersome return loop of wire to the battery. It also allows you to avoid tying into the boat's common ground, reducing the possibility of your boat's navigation lights going dark unexpectedly.
Measure the length of the route from the battery to the navigation light switch. Then, measure the distance the cable must cover to travel from the battery to the navigation light switch, to the navigation light farthest from the light switch. When you make your measurements, remember that you want to keep the wiring as high in the boat as possible, to minimize exposure to water.
Trim 12 inches of the cover from a roll of No. 3 tinned BC5W2 boat cable to expose the red power wire and the yellow ground wire. Strip a half inch of insulation from the end of the red wire using wire strippers and crimp a 3/8-inch ring connector to it. Strip a half inch of insulation from the end of the yellow wire and crimp a 5/16-inch ring connector to its end.
Move to the light switch panel. Trim the cover of the safety duplex cable to expose the red and yellow stranded wires. Clip the red wire and solder one end to each of the two lugs on the fused navigation light switch.
Pull the roll of boat cable from the switch to the first nav light. Clip the red wire in the cable. Strip a half inch of insulation from the wire. Crimp a three-wire connector onto both ends of the red wire. Push the navigation light's red wire into the remaining opening of the three-wire connector and crimp the connector.
Clip the yellow wire. Crimp a three-way connector onto both ends of the yellow wire. Push the navigation light's green wire into the third opening of the three-way connector. Crimp the connector. Move to the next nav light and repeat until you reach the final navigation light you wish to wire.
Clip the boat cable from the roll. Strip a half inch of insulation from the red wire and push it into a butt connector. Push the nav light's red wire into the butt connector and crimp the connector. Strip a half inch of insulation from the yellow wire and push it into a butt connector. Push the nav light's green wire into the butt connector and crimp the connector.
Return to the battery. Connect the red wire to the battery's positive terminal and the yellow wire to the battery's negative terminal.
- Disconnect the negative cable of the boat’s battery before modifying your boat’s electrical system, using a 5/16-inch box-end wrench. Lift the cable from the battery, move it outside the battery box and close the lid of the battery box. After the work is complete, reconnect the negative battery cable.
- Safety duplex cable uses yellow for its ground wire, so that you don't confuse it with the green ground wire used in 12VDC systems or the black wire used for AC power wires aboard boats.
- Test each crimp connection by grasping the wires on both sides of the connector and pulling.
- Never use household "Romex" cable as a substitute for safety duplex boat cable. Romex is a solid core wire that won't stand up to the rigors of life at sea.
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