An electrical fault on a boat is not a maintenance nuisance. It is a safety problem. The circuit that runs your cabin light also runs your bilge pump, and salt does not attack both equally โ it goes after the weakest joint first, quietly, over months.
Salt spray does not dry and disappear. It settles on terminals, fuse holders and connectors and stays damp, and damp plus oxygen starts eating copper. What you see first is a green or white crust. What you do not see is the wire turning black inside the insulation, conducting less with every trip.
Signs worth acting on the same day: green crust on terminals, a fuse that keeps blowing, a plug that feels warm after running, lights that flicker when the engine vibrates, electronics that restart on their own, and a bilge pump that sounds tired.
Buy tinned copper, not bare copper. The tin coating keeps salt off the copper and the wire stays serviceable for years. Bare copper goes black from the inside and crumbles when you move it. The price difference is small next to the cost of rewiring a boat.
Never twist two wires together and tape them. A twist creates a resistance point, resistance makes heat, and heat plus humidity destroys the joint faster than salt alone would. Crimp a proper terminal or butt connector, then seal it with adhesive-lined heat-shrink. Put a little dielectric grease on the terminal before assembly โ it stops water creeping up the strands, which it will do given half a chance.
The ground connection is usually the first to go, because it lives low down, out of sight, in the wettest part of the boat. When it weakens, current finds another way home through the hull or through nearby metal. That is when electronics start behaving strangely and stray current begins eating underwater fittings.
Ten minutes a month covers most of it:
Write down what you find. The catch log in B7R works as a boat notebook too โ note the fault you spotted and have not fixed yet, and it is waiting for you before the next trip.
Household tape is not a repair. Twisted wires are not a repair. Mixing wire gauges on one circuit is how you end up with a hot wire inside a locker. And never fit a bigger fuse to stop it blowing โ the fuse is there to protect the wire, and if you upsize it, the wire becomes the fuse, inside the boat.
A bilge pump that fails silently is the real danger. It does not alarm and it does not smoke. It just stops moving water, and you find out when you lift the engine hatch.
B7R is free on Google Play, with tides for Shuwaikh and Shuaiba, sea state, a fish guide, catch log, seasons, navigation tools and an SOS button for when something goes wrong out there: https://play.google.com/store/apps/details?id=com.q8dm.b7r