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Preventing electrical failures…

How many of you have these terminal block connectors on board ?..


How many times have I seen so called professional marine electricians using this type of terminal block….Pitiful isn’t it !

There are so many type of electrical connector – all claiming to be for marine use ….

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imageThe ML-XT Sealed Connection System by Molex claims to be the best sealed system in the market today, preventing electrical failures in critical wiring applications. Premium grade liquid silicone rubber (LSR) material ensures the ML-XT connector system meets J2030 requirements for advanced sealing. The thermoplastic plug housing forms a covalent bond with the LSR seal, resulting in an extremely strong interlock which prevents fluid ingress and seal loss or misalignment, even through repeated mating and unmating. ML-XT connectors offer a better seal design and a better rating (IP69K), and are drop-in replacements for other industry standard connectors currently available.

Heat shrink v Don’t Heat shrink…

There are so many pieces of advice on how to seal wires on a boat …

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Will you be sealing moisture in?.. will the end allow water ingress and corrosion? Have you twisted the wire tempting strands to fail?… have you taken into account the surface conductivity property?

Probably the best method to join two wires is the solder splice type of connector with both solder and heat shrink techniques applied at once plus adhesive to stop water/humidity ingress…


If you are using non-tinned bare copper wire don’t twist the stranded wires together…. try to push each bunch of strands into each other so that as many surfaces are in contact as possible from each cable. This is because of the strange property of electrons to try and travel mostly at the outer surface of any given cable….

Tinned v Not Tinned copper wire ….

Then there is the debate on whether to use tinned or not tinned…

On the lab bench and under ideal circumstances, bare copper is going to outperform the `tinned’ variety. It isn’t quite that easy. If it was, we would be done, end of discussion. However, you can’t have an “age old argument” if the situation was straightforward can you? I have experienced different results than the lab testing would suggest. My own testing has proven both types of copper can be right if you add in the missing variable…time. Fresh, new, bare copper conductor works great. Unfortunately, I have found that it will oxidize much more quickly than the tinned variety which leads to a degradation in electrical performance.…

To the naked eye, a copper conductor may appear to be smooth and uniform, however microscopic pits and cracks still exist and moisture can easily penetrate these imperfections. The hydrogen atoms present in the water vapour will combine with other elements to form acids which eventually cause even more metal to be exposed by enlarging the imperfections in the base metal. It gets even worse when sodium is present as in the case of salt water. Sodium accelerates the chemical reaction that forms the destructive oxide compound. As more of these atoms combine they weaken the integrity of the original metal making it brittle and crumbly, a process commonly known as corrosion.so in practice use tinned – if you can afford it !


How to crimp!..


CrimpingI had an email from a reader asking me about one of the links over here on the right hand sidebar under “Useful Info” – and it reminded me to look at some of my links again!…

One of the links that I just loved is from an author who goes by the handle “mainecrusing”. He has numerous “HowTo” pages here. There are lots of photos for each job and I have certainly found them very helpful – check out the one on crimping tools for example.

…”In this photo I have lined up some of my wire crimper’s. The one on the far left IS NOT A CRIMPER! I only say this because I have witnessed people putting together marine terminations with a pair of PLIERS!!

The next crimper, the one with the yellow handles, is a cheap hardware store quality crimper and should only ever be used in an absolute emergency.

The middle crimper is a decent quality Klein crimper though it’s not really well suited for much other than crimping non-insulated terminals. The fourth crimper is a good quality crimper, made by Ancor Products, and designed specifically for crimping marine or aviation grade heat shrink terminations. The jaws of this crimper are precision machined, and wide enough in cross section, to produce an excellent crimp. This crimper is also of the ratcheting type and will not release until a proper crimp has been made. The final crimper shown is another ratcheting type crimper but this one, set up with the jaws shown, is designed for insulated terminals. ….”

Mainecrusing also has a YouTube video channel although that appears to be of less help since he seems averse to actually speaking. He is obviously quite a guy – this link shows him replacing a diesel engine on his yacht – single handed!

On a related note to the “howto” of crimping is the issue of keeping joints clean and free of corrosion – perhaps one of the hundreds of connections that you didn’t do or that some “professional” did when the installed your chart plotter or radar …grrrr!

This is a list of techniques and products that you might consider:

  • Tin the wire – if you can access it and have enough spare wire to play with
  • Coat the joint with Vaseline or petroleum jelly – after cleaning the corrosion off with emery paper
  • Spray the joint with Conformal Coating – again, after cleaning if possible

Or use one of the combination grease + conductive materials type pastes :-


Wiring supplierFinally there are many obvious places to go to get electrical supplies – and many of us – me included have bought stuff in car accessory shops to save money. This eBay supplier – Genuinedealz – seems to have a lot of good feedback from people- they ship free in the USA and UPS to the UK.

Genuinedealz actually stock real marine grade parts, tinned wire, lugs, tools and is also a great place to compare the electrical properties of wire and accessories before you jump in and buy something.

Happy Crimping !