Generally speaking, improper wiring on boats abounds. The marine environment is a harsh one, and what may have sufficed on an automobile you tinkered with at one time, is no match for the incessant ravages of the salt water environment. This is especially so on older boats where multiple layers of electrical upgrades left by multiple owners can leave an owner perplexed.

And always make sure that you use marine-grade materials.  Marine wire has flexible, multi-stranded, tinned copper conductors. Tinned refers to the silver color coating that protects the wire from corrosion. Marine wire insulation should additionally be oil, water, and heat-resistant. Wire connectors should be double crimp, tinned copper, with a nylon (not vinyl) outer sleeve. Do not use wire nuts or simply twist and tape wire ends together. These methods cannot properly seal the connection, and can vibrate loose, leaving a live wire out of sight just waiting for something to send it arcing.

Solder can be a mixed blessing. Solder and tape connections that don't use mechanical connectors can fail by breaking. A good solder joint is nearly perfect. A bad one can fail completely. On tinned marine grade wire, excellent, reliable, repeatable splices can be made without soldering.

Adhesive-lined heat-shrink tubing is the marine electrician's secret weapon. Properly applied, this stuff will seal out 100 percent of the moisture in a splice. Additionally, it also makes it even harder to pull the splice apart. Beware of thin walled heat shrink tubing that doesn't come with an adhesive. These products will wick in moisture, and are easily damaged.

Butt Splices. You should cut and discard about two inches of wire to give you a new end to work with. First, strip off the length of insulation that will fit into the copper barrel of the butt connector. Use proper wire strippers that remove only the insulation and not the wire strands with it. Next, find the suitably sized nylon coated butt connector for the splice. Yellow is for size 10-12 AWG (American wire gauge), blue is 14-16 AWG, and red is 18-22 AWG. Slide the wire into the connector, making sure no strands are pushed back. The stripped portion of the wire should insert completely into the narrow section of the metal barrel. The nylon sleeve and the wider portion of the barrel should overlap the insulation of the wire. Making sure the wire does not lose this position, crimp the inner narrow barrel first and then the outer wider portion. The crimping should be done with very firm pressure.

Before adding the second wire to the splice, prepare it for the moisture seal. Use a piece of heat shrink that is the proper diameter to freely slide over the connector. Cut a piece long enough to cover the entire splice and overlap the wire insulation by at least a half-inch on each end. Slide the heat shrink over the wire and out of the way of the butt connector. Strip the end of the other wire in the connection. Insert this second wire into the barrel and crimp the connector. Test the connection with a very firm pull. It is better to have to re-splice it now rather than have the connection fail in service. Now slide the heat shrink back over the splice. Using a heat gun, heat the splice evenly by moving the heat source back and forth and around the splice. Once the tubing has shrunk to taken on the shape of the splice and the wire, and the adhesive has flowed out completely around both ends, the splice is complete.

Terminals. The best terminal ends are the closed ring type, which can't vibrate out if the terminal screw loosens. The screw or stud must fit in the ring. If the ring is too large, you will not make good contact, which is what all electrical systems are based upon. If the ring is too small the screw will bind in the ring. Avoid using plug in type male/female connectors. These are referred to as blade or bullet disconnects. These are difficult to seal and they often come apart too easily.

Crimping the terminal end is similar to a butt splice. Strip the wire back the same length as the small section of the barrel plus another 1/16 of an inch. Then slide the heat-shrink tubing over the wire and out of the way before placing the terminal on the end. Slide the wire into the correct size ring terminal until the strands exit the ring side of the terminal by a hair. Crimp the ring end of the sleeve first, then the wire side. Test the crimp with a hearty tug. Then slide the heat shrink tubing over the connector so that it just covers the protruding wires on the ring end of the sleeve and overlaps the insulation on the wire end. Avoid sliding the tubing over the ring area, as this will interfere with the screw contact. Next, heat the tubing just as you did with the butt splice. If any wire strands are visible at the ring end of the sleeve, seal them with an electrical sealant.

The Finishing Touch. Supporting the wire before and after the connector will reduce tension on the splice itself. Either bundle the spliced wire to other wires with ties or use wire clamps to hold the wire to fixed parts of the boat. If two adjacent butt splices must be made, stagger the splices by a couple of inches. Should the wires pull apart, they won't short against each other. In any location where moisture might wick down the wire and into the splice you should form a drip loop. Simply make a bend in the wire that will cause water to drip off of the wire before reaching the splice. After the new wire is run, it should be labeled on both ends.

So now if you add voltage to that rotted copper wire… and remember, a reaction will also occur without the presence of chlorine; but chlorine (that chemical that also eats stainless), a small atom and an excellent oxidizer, greatly accelerates the corrosion process.

Here's a website from the U.S. Coast Guard with electrical requirement mandates for small craft.

So, that shiny brown copper wire maybe a good price but do you really want to reach down into the bilge to redo that float switch at the worse time, or wonder why that navigation lights don’t work, working into the harbor at night, pull the anchor up by hand, and the start or kill switch on the engine won't work, etc.

Hanging by a Thread

I survey to ABYC voluntary “specifications” and at times had to write in my reports that the ball valves on a vessels thru-hull fittings do not comply with those specifications, especially those below the waterline. Some times that’s 20-30 ball valves! So what’s the difference? First, here’s what they look like.

                        Ball Valves                                        Sea Cocks              

That “base” or “plate” at the bottom of the sea cocks is the first difference. Also, most of the ball valves I have seen are “taper” threaded. Tapered threads were designed and invented to help a joint not to leak. That’s great but most thru-hull fittings are straight threads, like these.