Electrical system and generator

Check wiring, batteries, chargers, shore power and the generator. Electrical faults cause fires, and an old battery bank is a hidden bill.

Updated 24 Oct 2026 2 min read

Key points

Green corrosion on bare copper wire and tangled add-on wiring signal trouble.
Lead-acid batteries commonly last 4 to 6 years.
Test shore power with an RCD and check for a galvanic isolator or isolation transformer.

Wiring and panels

Open the switchboard. Wires should be labelled, tidy and secured, with no melted insulation.
Look for green corrosion on copper conductors. Tinned copper resists marine corrosion and bare copper does not.
Look for add-ons: extra circuits spliced into old ones, loose connectors and mismatched fuses.
Check the fuses and breakers are the right rating for each wire.

Batteries and charging

Age and type of the house and engine batteries. Lead-acid banks commonly last 4 to 6 years, depending on use.
Terminals clean, tight and protected, and the bank firmly fixed.
Charger, alternator and solar regulator charge to the right voltage for the battery type.
Lithium installations need a battery management system and a charger set for lithium. Ask who installed them.
Battery isolator switches work.

Shore power

The inlet, the cable and the plug are undamaged.
An RCD (residual current device) protects the AC circuit, and it trips when tested.
A galvanic isolator or isolation transformer protects against stray current corrosion in marinas.
Polarity is correct.

Inverter and appliances

Test the inverter, air conditioning, water heater, fridge and washing machine for running current. Note the noise and heat.

Generator

Hours, service history and the model's reputation. See Service history: what a seller should provide.
Starts, runs steady under load, and shuts down correctly.
Exhaust and water injection are tight, with no leaks into the bilge.
Sound enclosure intact and the mounts sound.

Test all navigation lights, the horn, the VHF, the AIS and the autopilot. Electronics date quickly, so ask when they were fitted. See Upgrading marine electronics.

Also useful at step 5 Mechanical survey and oil analysis

General information, not legal, tax or financial advice. Rules change; check your own case with a professional or ask us.