Wiring is secured in bundles and fastened to bulkheads; this protects against vibration and minimizes clutter in the workspace.

Nine out of ten times a bad connection will prove the root cause of any electrical gremlin you might discover in the DC equipment aboard your boat. Vibration, severe jolts from running hard in substantial seas, and corrosion induced by salt air or water intrusion can all lead to the failure of poorly constructed connections in your electrical wiring. To keep things humming for the long-term, it’s imperative you make those connections using the best materials and techniques available. Here’s how to do it right.

In the harsh marine environment only top-shelf wiring will suffice. Start by choosing good quality stuff, properly sized and color-coded for the job. Stick with American Wire Gauge (AWG) standard sizes made from stranded tinned copper with oil-resistant insulation rated at 105°C dry and 75°C wet or higher. This type of wiring stands up well to hydrocarbons in or around engines and bilge areas while also providing good corrosion resistance.

Selecting the proper size wire for a job requires you know two things. First, you’ll need to know the distance between the power source (battery, bus bar or circuit breaker) and the equipment being powered. Next, you’ll need to know the current draw of the item—this is usually clearly stated in the accompanying documentation. For example, if you were going to install a bait pump that draws 5 amps located 10 feet from the power source you’d need to use No. 14 wire for the circuit.

Whenever possible use wire with insulation color-coded to the type of circuit you are wiring. In our example, the negative wire to the pump should be black and the positive wire from the controlling switch to the pump should be brown. This follows the standard marine industry color-coding listed in the accompanying table.

Heat shrink tubin applied to heavy gauge wire and battery lugs.

With the proper wire selected, it’s time to make a connection. The pump used in our example likely has leads anywhere from 2 to 4 feet long coming from the motor. To join the conductors wire-to-wire requires a butt connection.

Several styles of butt connectors are available, but only one has all the right ingredients to hold fast and keep corrosion at bay—a crimp connector with integral heat-shrink tubing. Ancor Marine makes three different sizes of heat-shrink butt connectors specifically designed to connect one wire to another. They cover AWG wire sizes from No. 22 to No. 10. In our example, we’d use the blue connectors as they’re sized for either No. 14 or No. 16 wire. These butt connectors are made from tinned copper to maximize current flow and corrosion protection. They also have thick-walled adhesive-lined heat-shrink tubing to seal out water and relieve some mechanical strain.

Marine-grade, heat-shrink butt connector seals out corrosion.

To make the butt connection, strip off just enough insulation from each wire so it fits into the metal crimp—insulation should remain on the wire where it is contained by the heat shrink tubing. Make sure you use an AWG sized wire stripper so that you do not damage or cut any wire strands while stripping off insulation. Twist the strands together, then slide the first wire into the connector and crimp it in place with a properly sized crimping tool. Do the same with the second wire, then give each wire a pull to make sure they are secure. Now use a heat gun to shrink the tubing and lock it onto the wire insulation. You should see just a tiny bit of adhesive ooze from the shrink tubing end when it is sealed and seated properly. Make the connection with the remaining wires and you’re done.

When making connections to a bus bar or electrical appliance that has lugs or screws, you should terminate the wire with a ring-eye style connector. Again, I recommend using connectors with integral adhesive-lined heat shrink tubing. Ancor Marine makes heat-shrink ring terminals for wires from No. 22 to No. 10 with ring eyes ranging from a No. 8 screw, a common size on a bus bar, to the 3⁄8-inch lug you’d find on the positive terminal of a marine battery. Connections are made in the same manner as with the butt connectors—strip, twist, crimp and seal. When a captive screw makes using a ring-eye terminal impossible, try a flanged spade terminal instead. The turned-up ends will hold this terminal in place even if the screw works loose.