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Can a 4-Way be Added to Trailer Wiring for Light Bar on Boat  

Updated 01/19/2026 | Published 12/18/2025

Question:

Want to add a brake light bar on top of my boat for trailering. Wish to keep existing trailer lights working. Need a Y-adapter to the existing wiring of some sort to add the light bar wiring. Do you have any product recommendations.

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Expert Reply:

Hey Patrick, basically you would need to splice in an additional 4-way to the trailer's wiring so that your light bar can be powered. Easiest way to do that would be with a kit like the part # C58044 which you'd splice into the current trailer's taillight circuits. This will give you a 4-way for a light bar to plug into like the part # OPT65KB. How were you planning on attaching the light bar to the boat?

expert reply by:
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Jameson C
Jameson C. profile picture
Etrailer Expert

Jameson C.

1/19/2026

Hey Patrick, how did things go with adding the light bar to your boat using the 4-way splice kit? Your setup could be really helpful for others wanting to keep their trailer lights working too.

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