The electrical system on a used yacht rarely gets the attention it deserves during a viewing, buyers look hard at the engine, the rig, and the hull, and treat the wiring as something that either works or does not. In practice the electrical system is one of the more expensive things to put right if it has been neglected or modified badly over the years, and many of the warning signs are visible to anyone who knows where to look, well before a full survey.
This guide covers what to check on board before you commit, and what a proper pre-purchase electrical survey adds beyond a general viewing, so you go into a purchase with a realistic view of what you are buying rather than finding out afterwards.
Original wiring on boats built before around the mid 1990s is often single-insulated, undersized by current standards, or run without proper support and chafe protection, and by the time a boat is thirty or forty years old, a significant rewire is a realistic prospect even if everything currently works. Look at cable insulation where it is visible behind panels, in lockers, and in the engine space, cracked, stiff, or discoloured insulation is a sign of age and heat exposure rather than just cosmetic wear.
Look for evidence of DIY modifications, spliced joints outside proper junction boxes, non-marine automotive connectors, wire nuts, or cable simply twisted together and taped. These are common on older boats that have passed through several owners and are one of the more reliable indicators of the overall standard of electrical work carried out over the boat's life.
Battery age is usually knowable, ask for receipts, and physically check date codes on the batteries themselves where visible. A bank of unknown age with no supporting documentation should be assumed to need replacement soon, and priced into any offer accordingly.
Check what charges the batteries and how well: shore power charger, alternator and any split charging or DC to DC arrangement, and solar if fitted. Ask to see the system running, ideally with the engine started so you can watch charging voltage rise at the battery, and check whether a battery monitor is fitted and what it shows for the bank's actual condition rather than relying on a resting voltage reading which tells you very little.
Anode condition tells you a good deal about both galvanic protection and how the boat has been looked after. Anodes wasted unevenly, or entirely gone, suggest either a stray current issue or simple neglect, both worth investigating before purchase rather than after.
Look at underwater metal, shaft, prop, skin fittings, for pitting or unusual discolouration, and ask whether the boat has a galvanic isolator or isolation transformer fitted if it has spent time on marina shore power. Corrosion problems found after purchase are expensive precisely because they often mean investigating and fixing a cause, not just replacing the damaged part.
Boats accumulate additions over the years, extra electronics, an inverter, a fridge, solar panels, and how well those were integrated into the existing system says a lot about what else might have been done less visibly. Look for evidence of correctly rated fuses and breakers on added circuits, proper cable sizing for the length of run, and whether additions were connected into the existing distribution board or spliced in ad hoc.
Ask specifically about any electrical work carried out, and whether it was done by a qualified marine electrician or as an owner DIY project. Neither answer should automatically rule a boat out, but it should inform how much further checking is worth doing before you commit.
A general marine survey covers electrical systems only briefly, usually a visual check and confirmation that things switch on, because a full electrical inspection is a specialist job in its own right and outside the scope of most standard surveys. A dedicated pre-purchase electrical survey goes further, testing charging performance, checking bonding and earthing, inspecting wiring standard behind panels where accessible, and giving you a realistic estimate of what, if anything, needs doing and roughly what it will cost.
That information is useful in two ways, it lets you negotiate on price where genuine issues are found, and it means you are not caught out by a large unplanned bill for rewiring or a charging system replacement in your first season of ownership.
Not in detail. Most general surveys give the electrical system a visual check and confirm equipment switches on, but a full inspection of wiring standard, charging performance and bonding is usually a separate specialist survey.
Look for spliced joints outside proper junction boxes, non-marine connectors, cables run without support or chafe protection, and additions wired straight onto existing circuits without their own fuse. These are all signs worth flagging for a closer look.
Not on their own, but they should be priced into your offer if age or condition is unknown, since a full house bank replacement is a predictable near-term cost.
Badly wasted or unevenly wasted anodes point to either a stray current problem or general neglect, both worth investigating before purchase since the underlying cause can be more expensive to fix than the anodes themselves.
Yes, many electrical issues, wiring standard behind panels, charging performance under load, bonding condition, are not visible or obvious during a normal viewing, and a specialist check gives you a much more accurate picture before you commit to a purchase.
We carry out pre-purchase electrical surveys, checking wiring standard, charging performance and bonding, with a clear written report before you commit to buying.