Marine Electrical Splice - Boat Wiring That Lasts

Since Bob has got a re-wire job to do (he never did get it completed), I figured I'd put the correct way to do it here.  Many thanks to Boating and Sailing News for making this available.  So, for all you newbies out there, check them out.  They have fabulous articles on how to work on your boat the correct way, in addition to regular news.  BTW, there's more photos available there of the wiring if you need them.

 http://yachtpals.com/marine-electrical-9162

Boating and Sailing News 27 Oct 2010

As they say, fast cheap and good, choose any two.  Installers and manufacturers know that customers don't like to pay for painstaking, some say "anal-retentive" work.  We don't often opt for the item that will last generations if it costs five times as much as the one that will last until we sell it in a few years, and that includes boats.  In the case of electrical connections aboard, this issue of fast and cheap often manifests itself in the use of crimp-on butt connectors (quit your giggling) instead of a good quality electrical splice.  The butt connector takes five seconds, while the proper splice takes five minutes, so, as you can imagine, with most people's eyes on the bottom line, the butt connector is going to win out, even when they are almost predictably prone to failure in the marine environment.  So, who does a sailor turn to?  Why cowboys and astronauts, of course.

Not to put too fine a point on it, but the basis of this problem is that copper wire corrodes.  As most know, we use multi-stranded, tinned copper wire on boats that has heavy duty insulation, or at least that's what we should be using (pop open many "marine" electrics and electronics, and that's not the case).  The 'multi-strand' means that the wires can take more flexing and vibration, and the 'tinned' bit means that each of the multiple strands is individually coated with something much like solder, which helps protect the copper wire inside.  This so called "boat wire" is great stuff, but it's certainly not perfect by any means, and it can and will corrode quickly and permanently if not installed properly.

The problem with even "marine grade" barrel type butt connectors is that they just crimp down on the wire, usually along a line, and then don't seal it.  If the wire moves due to boat vibrations, it can work along that one line where it was crimped, and eventually break. If any salt or moisture is present (imagine that on a boat!), then given time it can and will wick up the unsealed wire ends and corrode the entire length of wire.  There are steps to be taken which will help with these issues, like putting dialectric grease on the wire ends and shrink-tubing over the whole connection.  However, if you're going to go to that trouble anyway, why not just do a proper job of it, and get rid of the butt connector entirely?

Fair warning:  There are plenty of people who will tell you the method described below is over the top, and it probably is.  After all, this is a double-redundant electrical splice that is suitable for space travel (more on that in a minute).  However, if you've ever spent hours chasing a bad circuit through a boat's bilge, or an engine room, or had to pull off a headliner to get to a rotten connection, you probably have said to yourself (and everyone within earshot) that you never, ever want to do that again.  Well, in that case, something "over the top" may be just what you're looking for. 

As usual, we like to turn to the wisdom of experts when it comes to these things, and in doing so we find more often than not that the old craftsmen got it right long ago, and the new techies need to learn it all over again.  In this case, however, the old craftsmen and the highest of high tech engineers agree, and it's only us "regular people" (I do use that term loosely) who are in the dark.  Since a boat is an inhospitable environment, let's look to other inhospitable environments, and see what others have done to conquer them.  For this example, let's look at the American West of the late 1800's, and, oh I don't know, outer space?

In the case of the American West, a company called Western Union needed to stretch telegraph cable all the way to the Pacific Ocean.  The wire came in spools, and the end of each spool had to be connected to the beginning of the next via a splice.  So, over thousands of miles, the guys making the splices got pretty good.  Then, over time, the wire would break (or be cut by outlaws!) and repairs were made by, you guessed it, splicing.  So, when a telegraph message was transmitted (with very low power), it was transmitted over many, many splices, so they had to be both very strong, and very conductive.  The resulting splice became known as the "Western Union splice" for obvious reasons.

NASA has some of the strictest policies around when it comes to its contractors.  A close eye on materials, manufacturing methods, precise specifications and minuscule tolerances is what it takes to put someone into space, and if even the slightest thing is overlooked (such as the materials in an O-ring), it can end in disaster.  NASA scientists examine and deliberate over every little bit of every little bit, and when it comes to splicing wires, the specifications are very exacting.  Thus, many are surprised to learn that one of the few acceptable splices for those planning on space travel is, drumroll please:  The Western Union splice!

Take two wires, cross them at a right angle, wrap one wire around the shaft of the other, and then repeat with the second wire.  This is the famous Western Union splice.  You'll notice that the splice tightens as you pull on it, and this means that the physical connection between the wires gets better with tension.  This is a great splice, and if you were working on a car, you could probably just wrap a little tape around it and never think about it again, but you're not working on a car, so this is just step one, or actually, step three.

Connecting Wires on a Boat (see top photo):

1.  Strip the insulation from a couple of inches of each wire, and twist the wire to make it easier to deal with.
2.  Slide an adequate length* of self-adhesive shrink tubing down one of the wires.  If you forget this step, you'll regret it.
3.  Join the two wires using the Western Union method.
4.  Solder the connection by heating the wire with a soldering iron until the wire melts the solder and wicks it into the connection.
5.  OPTIONAL:  Coat the connection and the last 1/4 inch of insulation with liquid vinyl "electrical tape" and let dry.  This will seal the connection even if the shrink tubing fails.
6.  Slide the length of shrink tubing over the connection and shrink it with a heat gun. 

*The shrink tubing should completely cover the liquid vinyl and extend at least 1/2" up the insulation of each wire.  For an über-ultimate splice, use two lengths of adhesive shrink tubing, one longer than the other.  Apply the shorter over the connection, and then the longer.

You may wish to reserve this connection for the worst environments on your boat:  The bilge, the engine room, inside rails and pulpits, etc.  Or, you may wish to use this only after a crimped-on connector has failed (which is less likely if you use adhesive shrink tubing over such connections).  After all, many crimped connections are just fine for years, and you may sell your boat long before the next one goes bad.  On the other hand, if you plan on going into situations where you have to rely on your boat (and who doesn't?), you may just want to be proactive.  An ounce of prevention, or a stitch in time, or however you put it - it's usually better to do a little extra work up front than pay for it later.