re: Functioning boat trailer lights

I agree. You’ll see so many trailers on the road with lights out.

If the harness is still good leave it alone. Go with led lights. Use the heat shrink style butt splices for the wiring, they sell them at auto zone and don’t come apart or let water/moisture in to corrode the wires. For the clearance lights where you use the quick splice connectors, add dielectric grease there. Make sure you clean the areas where the grounds go against the frame. Connect the ground off the harness by the plug to the frame of the trailer. It’s not supposed to ground on the ball of your truck. Follow those steps and you’ll be trouble free.