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Old 01-26-2004
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Chris Brignoli is on a distinguished road
Keeping Wiring Woes at Bay


A few simple tools and some know-how is all it takes to keep electrical devices working, but if you feel like you're getting in over your head, consult with a professional.
Imagine you take a walk through your newly acquired boat with a marine surveyor. Looking at the voltmeter, he notices that your new batteries are almost dead, despite the fact you just charged them two days ago and no equipment has been left on. He opens the bilge-boards and notices a green, powdery residue sloughing off your thru-hull valve that indicates serious corrosion. Reaching in, he tugs on a skein of wires running through your oily bilge water, hanging below your propane locker. A splice pulls apart, and for a moment blue sparks fly. He shutters. Looking at the separated splice he notices the copper has turned a greenish black. Later he tells you that he's not surprised to hear that some of your important electronics aren't working. And then the next day, your marine electrician informs you that all of these costly problems could have been avoided at the start with a little attention to detail.

Safety First    If you recognize yourself in the above scenario, then you should be aware that boat owners who don't have a basic understanding of electrical theory should really hire an electrician. Electricity demands respect, and if you don't know what you are doing, mistakes made in this department can injure or kill you. At the very least they can fry your expensive electronic equipment. However, if you do chose to rectify electrical problems on your own, take a few precautions before you get started: Make sure that the inverter, if you've got one, is off and the shore power is disconnected. And be certain that the power to the circuits that you are working on are disconnected at their source. Towels should be thrown over solar panels, and wind generators should be disengaged. Again, if you have any doubt about your abilities, stop what you are doing and find professional help.

Tools and Materials    Generally speaking, improper wiring on sailboats 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. Start by using the right tools. Wire strippers and crimpers should be sized for marine grade wire and connectors. The crimpers should be the ratcheting type that apply the proper amount of pressure to the wire connector.


Electrical wires and components lead a rough life in the corrosive salt air.  Using marine-grade wire and connectors will keep you from the onerous task of looking for a short while underway.
And always make sure that you use marine-grade materials. For wire, heat shrink, and connectors, a safe bet is to use Ancor brand wiring products. Marine wire has flexible, multi-stranded, tinned copper conductors. Tinned refers to the silver 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. On non-tinned copper stranded wire, in wet locations, soldering or replacing the wire is worth considering.

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.


A house is not a boat. A house is a stable thing. Twisting two wires together and putting a plastic cap on them might be considered up to code on shore, but aboard a boat that pitches, rolls, and yaws, any wires not securely fastened can bring about serious consequences.
Butt Splices   
When starting your splicing project, you should cut and discard about two inches of wire to give yourself a new end to work with. If you have to work with non-tinned wire, it should be cleaned to a shiny copper with isopropyl alcohol and an abrasive pad.

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.

"Test the connection with a very firm pull. It is better to have to re-splice now rather than have the connection fail in service."

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. If you must use them, they can be slightly crimped to increase their friction.


First test a terminal by pulling on the connector. Then seal the deal with shrinkwrap, and you can very likely forget about ever coming back to check for faulty wiring.
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.

I don't recommend that you use electrical tape to seal wire connections. The glue used in electrical tape seems to melt in the marine environment, and using the proper connectors along with heat-shrink tubing will reduce the need for tape. However, if you need it for repairs, I recommend that you use 3M Super 33 tape. This product uses better adhesive, and the tape functions well in the cold and heat. Alternatively, 3M Scotch No.23 is an excellent non-adhesive tape (the rubber sticks only to itself). A final trade secret is to use wire ties over any tape, which will prevent it from unraveling.

"It's very important that you try to keep all wire, especially splices, out of bilge water areas."
 Electrical spray coatings or brush on sealants can be used to cover exposed terminals keeping the corrosion at bay. But it's very important that you try to keep all wire, especially splices, out of bilge water areas. A splice that is regularly under water will almost certainly cause electrical leaks. With time, even marine-grade wire insulation seems to dissolve when submerged in a soup of oils and seawater.

Suppose you want to connect the fused red wire from your new CD player to a terminal screw on an empty breaker switch. You determine that the screw size is No. 10 because it fits snugly into the ring connector marked No. 10. Next you examine the red CD wire and determine that it is marked 12 AWG. Happily, you refer to this article and note that a 12 AWG wire needs a yellow connector. Make sure to slide the heat-shrink tubing over the wire before you insert the connection and crimp. You crimp twice, tug firmly, and then apply heat to the tubing after it's in place. You connect the ring to the breaker with the No. 10 screw, support the wire with wire ties and clamps. Then you spray on some electrical coating and smile knowing you are well on your way toward being able to confidently sip daiquiris while lying at anchor and listening to your favorite musical artists on your very reliable sound system.

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