How to Wire a Marine Trailer
- 1). Secure the four-pole harness to the tongue of the trailer with cable ties. Leave enough length so that the harness can reach the vehicle's electrical receiver.
- 2). Sand a small section of paint off the trailer's tongue. Attach the white wire from the harness to the bare metal with a drill and self-tapping screw. The trailer's lights use the metal frame as their ground connection.
- 3). Run the brown wire from the harness along the frame to the first marker light. Connect the brown wire to the power wire for the light with a Scotchlok connector or equivalent. These work by placing one wire in each slot and closing the gate until it locks.
- 4). Run the brown wire to the next marker light and connect it in the same fashion to its power wire. Repeat this process until all of the marker lights are connected.
- 5). Run the harness' yellow wire along the frame to the left turn signal. Connect it to the power wire with a Scotchlok connector or equivalent.
- 6). Run the harness' green wire along the frame to the right turn signal. Connect it to the power wire with a Scotchlok connector or equivalent.
- 7). Wrap all of the connections in electrical tape. Secure the loose wires to the frame of the trailer with cable ties.
Source...