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How To Install Electrical Items


Without Burning Your Boat to the Waterline

Adding electrical equipment is sometimes more than just running a new circuit. If the main panel doesn’t have the extra capacity, it has to be upgraded. This one wasn’t and overheated, causing a fire (Claim #0303974).

The flow of electrons moves completely unnoticed, smoothly, silently, and peacefully through the wires on your boat — until it doesn’t. The interruption of serenity could result from the improper installation of an electrical item, a poor wiring connection, undersized wiring, or old age and wear, but the end result is the same: the potential for a catastrophic fire.

How electrical items are wired and installed in your boat is incredibly important, yet this job is often tackled by inexperienced do-it-yourselfers. While we love working on our own boats and encourage others to do so, let’s spell one thing out, right up-front: if you have any doubts about what you’re doing, leave these jobs to a professional marine electrician.

Meltdown Mayhem

When the owner of this boat added a light fixture, he neglected to add a fuse to the circuit. Fuses protect the wires from overheating and without one, chafe or a defective fixture can cause a fire (Claim #9800883).

“The most critical part of installing electrical items is the wiring, and I’ve seen the results of substandard installations firsthand,” said Capt. Bill Hooper, an ABYC-certified marine electrician and founder of Blue Frontier Marine ( in Salisbury, Massachusetts. “On one boat I worked on, the customer had used black wires all over the place. He unplugged everything over the winter, and forgot which black wire was which while the boat was laid up. In the spring, he hooked the wires up backwards, and smoked the entire electrical system.”

Fortunately, the best way to prevent experiences like this is simple, whether you’re a professional marine electrician or a DIY boat owner: Regardless of what you’re installing, be it as weak as a tiny LED courtesy light or as potent as a 100-hp bow thruster, follow ABYC’s wiring standards. “That’s what they’re there for,” Hooper says. “Following the standards is key.”

Capt. Ric Corley, a marine surveyor in Panama City, Florida and a certified marine investigator who has over 40 years of experience and almost 6,000 surveys under his belt, also believes strongly in adhering to the ABYC recommendations. “This is one of the biggest problems in the industry when it comes to installing anything that runs on electricity, even in some new boats,” Corley said. “People use the wrong types of wires, the wrong sizes, the wrong colors, and the wrong connections all the time. Someone may be a good house electrician and know just enough to get themselves into trouble, but boats just don’t work like houses. If everyone followed the standards, they’d be a lot better off.”

Why is electricity so finicky on boats? Vibration, moisture, and corrosion are the main reasons. These factors work together to make the marine environment far more difficult than it is on dry land, when it comes to harnessing electricity and feeding it to your accessories. To understand why, you first need to understand one thing about the power surging through those wires in your boat: It’s trying to escape. To keep that power where it belongs, we encase our wires in a non-conductive insulation. This is where vibrations come into play. They can cause the insulator to become chafed, a problem that grows worse with age. That’s why one of the ABYC standards calls for wires running through or against a bulkhead, stringer, or other sharp edge to have chafe protection.

Another way insulation failure can wreak havoc is due to “wet tracking,” which is a problem common in the moist environments. When the insulation’s surface becomes wet, it can allow a small amount of current to start flowing along its surface. This can cause carbonization (as can exposure to a heat source, such as a wire rubbing up against a hot engine block), which turns the non-conductive insulator into a semi-conductive material.

Vibration, moisture, and corrosion all work together, however, to cause problems at the wiring’s weakest point: the connections. Remember that as electric current flows through any conductive material, it creates heat. When you have a loose or corroded connection, it causes increased resistance, which in turn causes increased heating at the contact. This can form an oxide, and the oxide then conducts current — but with considerably more resistance than that of the wires. The net result? Even more heat is created, and eventually, it can become hot enough to cause the metal to glow. If any combustible materials are nearby, a fire starts. In fact, poor connections are one of the main fire starters on boats. Overloads and spark-producing arcs happen, but much less frequently. So when it comes to any type of electrical installation, making good connections with crimp connectors protected by heat-shrink tubing is extremely important.

Amping Up

Wire nuts like these have no place on a boat. Designed for solid core wire, which also should never be used aboard, wire nuts cut into stranded wire, damaging the connection and potentially causing a fire.

How do you know when an installation job is too much for you to tackle? Again, when in doubt, defer to the pros. That said, the nature of the gear being installed has a lot to do with just how significant a threat it presents.

“With items like chartplotters and fishfinders, the amperage draw usually isn’t enough to present what you’d call a huge danger,” Hooper explained. “But with something like a windlass or a powerful appliance, the installation should really be done by someone who’s properly trained and certified.”

And while most fires relate to wiring, other aspects of the installation job can also cause problems. Making sure heavy items are completely secure and can withstand the vibrations they’ll be subject to on a moving boat is imperative, for obvious reasons. Other common errors that cause problems include installing an item in an area that doesn’t offer sufficient ventilation, which leads to overheating; failing to install the proper breaker(s) and fuses in the appropriate location(s); installing appliances where they may be subject to future water damage; and installing items that don’t belong on a boat in the first place.

“There’s a reason marine grade costs more,” Corley said. “A third of a cup of gasoline in your bilge is like driving around with three sticks of TNT onboard, and people sometimes try to save money by using automotive or home-improvement items on their boat. These are intrinsically dangerous because they don’t have spark protection. If there’s gas down there and something makes a spark, the boat blows up. In one case I investigated on Massalina Bayou, because one person didn’t follow the right standards, they almost burned down an entire marina. Several boats were tied together and fire quickly spread from one boat to another. If they hadn’t cut three boats loose and pushed them out to burn in the harbor, the whole place would have gone up.”

No one wants to see their boat aflame, much less be responsible for setting other people’s boats or a marina on fire. So anytime you need an electrical item installed, make sure to follow ABYC standards, know your own limitations, and don’t be slow to call for a professional. Keep that electricity where it belongs — moving quietly and unnoticed.

Electrical Boo-Boos — The Worst Offenders

When the owner of this boat was installing a new circuit, he neglected to attach the ground wire properly. Eventually, the connector began arcing and caused a fire in the electrical panel.

Marine surveyors often mention the same practice as one of the worst ever seen at sea when installing electrical devices: The use of wire nuts. Wire nuts work by digging into solid core wire to make a strong connection. But wires on boats are stranded and using wire nuts destroys the strands, actually weakening the connections and potentially causing enough heat to cause a fire.

Other commonly seen offenses include:

  • Improperly sized or colored wiring
  • The improper use of lamp wires, speaker wires, and other odds and ends meant for a specific purpose
  • Using solid wire instead of stranded wire
  • Mounting automotive engine parts on a boat
  • Improper breaker location

BoatUS Editors

Contributor, BoatUS Magazine