Lighting Tips for Trailers

Chris Riley by Chris Riley Updated on August 6, 2019. In

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One of the most aggravating aspects of trailering boats is the total unreliability of trailer lights. IÂ’ve never owned a boat trailer that didnÂ’t eventually have light problems. These usually start with little irritants that take a few minutes to repair and end up with the entire wiring system being ripped out and replaced, often late at night before a long-awaited vacation at the lake. This activity is accompanied by crawling around under the boat locating the grease spots in the driveway and numerous burns from hot drop lights.

On the bright side, (pun intended) it does explain why every auto-parts store carries trailer-wiring kits. In fact, research has shown that there are 4.3 wiring kits manufactured for every trailer in the country. If you think it canÂ’t happen to you, remember all those kits. The market is there.

There is a way to slay those electrical demons permanently. The biggest problem is that electrical connections and water are natural enemies. Water has been know to lie in wait for millennia for an opportunity to corrode even one crimp connector. The obvious solution then, is to keep the two antagonists separated.

One of the easiest and cheapest ways is with a light bar. This one is portable and easy to make. Construction can be done on the comfort and convenience of your kitchen table. That is, if your spouse is away. Otherwise, the garage is a safer alternative. Trust me on this one. If I told you that jumping into a running cement mixer wasnÂ’t a good idea, you wouldnÂ’t need to try it for yourself would you?

The parts are plentiful and inexpensive. First, youÂ’ll need a bar that can be easily mounted and removed from your boatÂ’s transom. Depending on your boat, a roof rack with suction cups might work. Never totally depend on suction cups. Use an additional method of securing the bar. I like lines to the stern cleats. Your boat may have different solutions. Just be sure the lights wonÂ’t be bouncing off the freeway as you tow.

The bar may also be constructed of schedule 40 PVC, aluminum pipe, or even wood. IÂ’ve seen one made of oak, beautifully finished with teak trim. All the pieces were attached with concealed screws and wood plugs. It was as much a work of art as a practical solution to trailer lights.

YouÂ’ll also need a length of four-conductor cable long enough to reach from the light connector on your car to the stern of your boat as it sits on the trailer. Get enough for several feet of slack. Use rubber-covered cable with twisted strand wires, not cheap single-strand doorbell wire. The cable flexes a lot and a broken wire inside the cable is not fun. Get the good stuff to start with and you wonÂ’t have to replace it in a couple of years. If you use good components everywhere youÂ’ll be able to move this bar from boat to boat over the years. Build this right and youÂ’ll include it in your will.

I personally favor soldered connections, but crimp connectors are also very reliable when they’re installed correctly with the proper tool. For those of you thinking that this might be an excuse to buy some new tools you’ve been coveting–well, when your spouse asks, you didn’t hear it from me.

I cover all my electrical connections, soldered or crimped, with marine-grade silicon. I do tow in the rain occasionally. You will, too.

When you buy the trailer lights, you can save a little cash because you wonÂ’t need the sealed marine units. Just make sure the bulbs are the common automotive type. They will burn out. YouÂ’ll want replacements to be readily available.

Mount the lights on the bar. Wire the lights to the cable, taking note of the color code. YouÂ’ll have to have a ground wire as thereÂ’ll be no metal-to metal connection between the car and the lights. Make sure when you wire the lights that there is a ground wire as part of the connector on your car. Many installations omit this and depend on the trailer hitch to be a ground connection. This is a bad practice and a major cause of the lights working poorly or not at all. Attach the connector plug at the other end of the cable and youÂ’re in business. When you string the cable along the boat, ensure that it wonÂ’t come loose and drag on the highway. YouÂ’d be amazed how this accelerates wear on the cover. Even a Sunfish has enough cleats and projections to secure the cable. DonÂ’t get so complicated that this is a chore to rig, though. The idea is to simplify your sailing life.

Diagram 1 is a schematic of the wiring. Note that, on most cars, the brake lights are actually both turn signals operating at once. If yours are separate, they should still be wired into the connector as shown. Otherwise, youÂ’ll need separate bulbs for the brake lights.





Diagram 2 is a typical construction for the light bar. The eye bolts are to secure the bar to the transom. Boats and equipment are different, so your version may vary.


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