Cairns Marine Electronics

Most faults I see that are a caused by a wiring fault, is usually due to the use of standard copper wire or not using quality materials to seal the wiring from external elements.

Copper will oxidize slowly, even in a desert, however up here in the wet tropics and sea air, copper wiring will go black and not last long when exposed to the elements.

I always use copper tinned wire for wiring applications requiring 8mm wire size or less, as these wires are significantly more corrosion resistant, which dramatically increases wire life span, and are also readily available around town. Most chandlers will have up to 6mm copper tinned, however for 8mm you may need to make a few calls. I buy mine online. Get the sheathed copper tinned, as the additional covering will help stop wires wearing through another wire (yes I see this occasionally), or when going through a bulkhead / wall. It will also protect the main wires from UV / elements and keep the inner wires intact - even after many years exposed to the elements. Many standard automotive wires will not last in the sun / sea air as the plastic coating will crack, even after just a few years.

It’s also best practise to use split cable loom as this will increase its usable life and will drastically reduce the risk of electrical shorts, open wires or even fire.

Copper tinned wire for engine cranking is usually hard to get, however copper will still work fine as long as you seal the wires perfectly. Generally small boats may use 25mm (3B&S) medium boats will use 35mm (2 B&S) and large will use 70mm (0B&S) for engine cranking. Once again, I prefer to use the double sheathed wire. I sometimes use heat shrink however I prefer to use self-amalgamating tape.

Most recreational boats have their battery undercover, but still outside, so it is really important to use a quality sealing material. Heat shrink with glue is ok, however these can be prone to failure if not enough heat is used or a too large of one used. I prefer to use the thin self-amalgamating tape with white backing plastic (see pic). The reason I like this one is because when applied correctly, it will last for donkeys years, even if the wires are sitting in salt water, like in the bilges. It is really important that self-amalgamating tape is applied with clean DRY hands, free from grease. That is why the white backing is good as it keeps the tape clean next time you want to use it. Also make sure you stretch it to almost to the point of snapping, as this improves adhesion. You will likely have a big thick bit when starting - that’s ok as long as you go back over both ends with the stretched tape. It may not be as pretty as heat shrink but it will last.

I always solder to join wires and then cover with self-amalgamating tape. If joining to an existing copper wire, sometimes you have to cut well back to see clean wire. It is not unusual for the entire cable lengths to be black from oxidation. I have seen wires running the full length of a 30 metre boat that required replacement. Often you can clean the copper - I usually scrape it clean, then use plenty of flux and solder to get a firm solder joint. Join the other wire to it and cover with self-amalgamating tape.

I avoid joiners like waterproof solder seal sleeves, as I often see these fail as well. They sometimes do not have enough solder in them to “soak” all the way through and they are made with low temp metals such as Bismuth, Indium and Cadmium mixed with the lead. These metals are brittle and will crack if work hardened from movement.