Boat Wiring Is Not Car Wiring. Honest.

Believe it or not, the electrical system in your boat faces a foe more sinister than the ravages of time or the harshness of the marine environment. Your electrical system’s greatest nemesis might be staring back at you in the mirror each morning as you brush your teeth.

Yes, you. Joe Saturday. Mr. DIY.

You see, in a former life, I was a parts guy. I worked in parts stores and a GM dealership for more than 10 years. I have met Joe Saturday and he is evil. Well, probably not evil, but if a guy is in an auto parts store looking for boat parts, he is cheap.

The logic goes something like this: “The boat’s got a Chevy motor in it. They’re all the same.”

Boatowners who want to do some of their own wiring should at least have a basic kit with high-grade marine connectors, like the ones sold by Ancor.

Uh, no. They are not all the same, so repeat after me: Boat parts for boats. Car parts for cars. This is important in a lot of places on a boat, but  it’s critical when it comes to the starter and alternator. Marine starters and alternators are ignition-protected, which means they are designed not to allow a spark to be emitted from the device, so that if there’s a flammable mixture of air and gasoline in the engine compartment, it will not ignite that surrounding atmosphere. Why is that important? For the same reason you run the blower before you start the engine.

If an alternator or any electrical appliance is not ignition-protected, and you for some reason have fuel vapors in your engine compartment and you crank that engine over, if there’s a spark, it could explode. That’s bad.

But it’s not just putting car parts on boats that will sideline you or perhaps make your boat go boom, it’s components that were not installed properly at the factory or add-ons that have been cobbled together by owners. It’s also wiring that isn’t large enough to perform the job, household wiring, automotive connectors, and improper support for horizontal wiring runs.

A common culprit is stereo installations. These add-ons must be done with the same proper marine connections as any electrical equipment on board if you expect it to last. That means screw-type terminals, heat shrink to protect crimped wiring, and proper-gauge wiring to power the unit and deliver the sound to the speakers. Without the proper materials, three months down the road you’re totally dissatisfied with the sound quality and reliability because the connections keep falling off.

As an extra measure of protection, treat your boat’s wiring with a good protectant. A litany of such products line the shelves at auto and marine stores, but one that stands out is Boeshield T-9, which was developed by Boeing. It performs from minus 40 degrees to 250 degrees Fahrenheit, which is not impossible on a boat if you consider winter storage and summer temperatures under the engine hatch. Boeshield T-9 is a combination of solvents and waxes designed to penetrate metal pores, dissolve minor corrosion, and leave a resilient waxy coating that lasts for months.

It’s available online or at West Marine. You might also find it an auto parts store, and that’s probably one of the few things for your boat you should buy there.

Brett Becker


  1. very informative article. should be taken as the gospel for boat owners. as a owner who does a lot of his own work on his boat I have followed to directions of this article to the letter on all my repairs from stereo installation to engine work on my boat. out in the middle of the sound or the straits of Juan De fuca is not the time or place to have your motor quit due to electrical problems..for one thing floating along in the current in the shipping lanes can get very nerve racking when your dead in the water and big ships are bearing down on you and your motor won’t start and your VHF radio won’t work!!! bad news as those ships don’t slow down or change course very quickly and they are bigger than you!!!

  2. Jason Adams says:

    Thanks for this article. I think, most of the time, people who are new to boating thinks that car wiring is just like a boat wiring. Although, they are almost the same but it’s not. Marine expert is very aware of this. I hope those people who are new to boating, can see the difference. For safety purposes also. Really informative article. Thanks again. :)


  1. […] Becker at Boat Trader has posted a good column about boat wiring. Believe it or not, the electrical system in your boat faces a foe more sinister than the ravages […]

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