My experience is somewhat different. I suspect if your boat sat in a marina for its life time and only went out of the marina on nice sunny days with gentle seas and light winds normal copper wire would suffice."Tinned Wire vs. Untinned
I get a lot of questions regarding tinned versus untinned wire, with many people believing that tinned wire is the only choice viable in the marine world.
Let there be no doubt, the tinning has no impact on amperage-carrying capability, it’s there to help mitigate corrosion migrating along a conductor under the insulation jacket via capillary action. There are tens of thousands of boats plying the waters of the world using untinned wiring that provides good service, and this has been true for decades!
Untinned copper wire (left) is used in boats with good results, but tinned wire (right) is better able to resist corrosion, both at terminals and in capillary action along the wire.
Is tinned better? Sure. But is it a game changer? I would argue no, as long as you keep the ends of your wiring away from exposure to water, which is generally considered good practice anyhow.
Marine-Grade Wiring: Give Your Boat the Good Stuff - boats.com
Well tinned wire can corrode too in those circumstances if they get wet.
Trying going to sea. If the weather is bad enough you will get water in your bilge. I read a good account once of a Jen 45 pilot house who got mixed up with some very nasty weather. Thr boat leaked from every hatch, portlight and window. It wasn't an old boat but bad weather puts considerable strain on everything. Green water has a habit of making its way past hatch seals
This is often quoted but my boat was originally wired with solid core domestic cable and most of it has lasted over 50 years. It is not a particularly dry boat either. The pvc insulation is extruded tightly around the copper and so water cannot migrate down the cable. Also the surface area of a solid core is less than multistranded and so minor blackening can be scraped off and the connection remade. If the cable is adequately supported then fatigue is not a problem at least at the vibration levels I would find tolerable in my boat.
I'd be surprised if you did find it; mains voltage in the UK requires double insulation and there is little call for single core tinned wire given installations need at least 2 cores.
Production boats are manufactured to a price.
Loads of cables for the offshore industry. If you follow this link you will find one to thirty cores from 1mm2 to 630mm2. They do tend to have all the cores the same colour with embossed numbering which might cause confusion if you are expecting harmonized colours for your mains.
Double Insulated cable is common in a domestic environment, but a large percentage of commercial and the majority of industrial buildings are wired in single core cable contained within trunking and conduit.
My original cabling installed in 1980 is in great condition. High quality tinned cable. A typical three core cable is individually insulated, then sheathed in rubber then sheathed in PVC. The only downside is the PVC has hardened over time
2.5mm square cable is suitable for ring circuits.Try building a yacht from scratch and see if the cost is peanuts!
