Recommended 4-Pole Trailer Wire Harness For A Boat Trailer
Updated 02/03/2026 | Published 06/24/2024
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Question:
I have a boat trailer with a 4 pin flat connector with 8 wires coming out of it. The trailer frame is enclosed tube steel with holes and rubber grommets where the wires come through to the marker and tail lights. Im assuming each light is separately grounded thus the 8 wire set up. my question is...if I replace it with a 4 pin 4 wire set up, is that the correct way making sure each light is grounded to the frame with the mounting bolts or screws? I am trying to go all submersible LED lights on the trailer Thank you!
asked by: Jim B
Expert Reply:
Hey Jim,
Without actually testing it I can't say for certain what the functions of your 8-wire connector are but yes, you could still switch to a 4-pole 4-wire harness since this is a boat trailer go with a wishbone-style harness like the Optronics # A35W42B. This harness just has a second running light wire so that you don't have to splice on a jumper wire to run from one tail light to the other and with how it's separated you should be able to easily push it through the frame all the way to the lights. You'll ground the white wire on this harness and then ground the lights directly to the frame.
If you haven't purchased the lights already then I recommend the Optronics LED Combination Trailer Tail Lights # TLL160RK. These are LED and designed for marine applications. The ground wire for these comes with a ring terminal that you can just run directly to the mounting bolts to ground the lights to the frame.
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Robin H.
2/3/2026
Hey Jim, how did the wiring swap go with the wishbone harness and LED tail lights on your boat trailer? Were you able to get everything grounded cleanly to the frame? Your results could really help others upgrading to submersible LEDs.