WIRE GAUGE?

Q:

Doc, how important is wire size, and where can I find out what size wire is best?

John Antowski

Chicago

A:

Undersize wires seem attractive to some boaters because thinner wire costs less, but using undersize wire is a bad idea for several reasons. These reasons are related to the fact that thinner wire means more resistance. More resistance results in voltage drop, meaning lights burn dimmer and pumps spin slower. More resistance can also create a fire. And thinner wire is more subject to degradation via the ravages of corrosion and vibration. As a general rule, the longer the run, the larger the gauge of wire that is required for safety and good performance. The American Boat and Yacht Council publishes charts for selecting the proper wire gauge based on both 3 percent voltage drop (critical circuits like bilge pumps) and 10 percent voltage drop (noncritical circuits like cabin lights). You can search for these online, or get the ABYC Wire Sizer app ($4.99) for iOS and Android.