Basic Wiring

circuit breakers, and fuses. We will even discuss a few basic electrical repairs you can make on your boat.

If you own a boat that’s more than a few years old, it may not comply with all of the standards outlined in the ABYC’s Recommended Standards and Technical Information Reports. This is not a cause for immediate concern. These standards have evolved over the years and have been revised as new materials and technology became available. The tables, charts, and recommendations in this chapter and in the rest of this book reflect the recommendations of the ABYC at the time this book was written. Wire types and circuit-protection ratings are not likely to change in the foreseeable future. On the other hand, there could be breakthroughs in insulation technology as newer and better materials are developed, and a technological advance might create a new circuit breaker that will be better than the ones we use today. If either of these events should transpire, rest assured that the ABYC will take a close look and make appropriate recommendations based on what they see.

The ABYC electrical standards go into great detail on the minimum criteria for both DC and AC circuits used on boats. Basic considerations include the length of the wire, nominal voltage, amperage, routing of the wire, insulation temperature rating, and the chemical environment to which the insulation is likely to be exposed. One additional consideration is the conductive material used in the wire.

Wire Types

Electrical wire comes in a variety of types and conductor materials, but by far the most common conductors are made of copper. Aluminum is used in some automotive applications, but aluminum conductors of any type, including terminal strips and studs, are strictly prohibited in the ABYC electrical standards. The soft aluminum used in wiring corrodes easily (unlike the hard aluminum used in boat hulls), and it can become brittle and break when subjected to the constant vibration and flexing of a typical boat underway. It also isn’t as good a conductor as copper, and the added resistance means that it gets hotter quicker than copper. Don’t ever use aluminum wire on your boat, and if you find any already installed, immediately remove it and replace it with copper wire.

In addition, solid wire, especially the solid-copper Romex that’s used in house wiring, is never acceptable on boats. This precludes the use of many wiring types found in hardware stores or in home-supply houses. Solid-copper residential wiring breaks easily under vibration, and it was never intended to withstand the exposure to moisture or oil and gas fumes found on today’s boats.

According to the ABYC specifications, the only acceptable material that may be used for boat wiring is stranded copper. Although not specifically mentioned in the standards, good-quality boat cable today is often tinned as well. This means that every strand of copper in the wire is coated with a thin layer of tin (solder, actually) that impedes the formation of corrosion. Copper doesn’t corrode in the same way as such materials as aluminum and steel, but forms a thin layer of oxidation that’s highly resistant to electricity. The tinning slows and reduces the formation of this oxide layer and greatly reduces the incidence of problems caused by corroded wires. It’s also much easier to solder than untinned wire.

Tinned copper wire will pay off in the long run. Initially it may seem a bit expensive compared to stranded copper without tinning, but on a boat, where corrosion is a constant battle, the tinned wire will hold up far longer than would untinned wire. The tinning does a great job of resisting corrosion at terminals as well as preventing oxidation from migrating up the wire under the insulation, a common problem with untinned wire.

Stranded copper wire is available in several types. The chart in figure 4-1 on page 42 is taken from section E-11 of the ABYC’s Recommended Standards and Practices and illustrates several additional points. Notice that the American Wire Gauge (AWG) standard is used to designate wire size. You may encounter wires on your boat that carry the Society of Automotive Engineers (SAE) designation. Quality marine-grade wire with an AWG-size is often larger in