Accessories like reversing lights

I suggest, espec in marine conditions , to run cables down each side from the connector....to the lights each side. Then across a trailer cross member between the lights.
 If one side / connection fails you have a back up circuit.
 Dont use cable heavier gauge than required

 Make sure that you have more than needed excess length cable between trailer and where plugs into vehicle....not all vehicles have the plug the same side position....


Make all connection tidy... bit of practice getting stripped the right length.. so strip a little more than think and cut to length as needed.

When have all sorted , working...and covers off.. a light spray of of aerosol lanolin, connectors, bulb holders etc to slow down corrosion dramatically.
 A good quality insulation tape on the outside of lights, tight around the join between the lens and the back.

Regular maintenance after each trip a quick spray with a CRC type product of connectors.. hitch padlocks, roller, wheel nuts etc.

The lanolin aerosol is not cheap... also use... even mist spray couple times a yr on a cold dry engine and the hydrolic tilt area.
Do NOT get any of these sprays on the sacrfical anodes