When a boat generator runs but the boat still has no power, or trips, surges or will not start, the problem is often electrical rather than mechanical. We check and repair the electrical side of generators: output and voltage, the changeover between shore and generator supply, start and control circuits, earthing, and how the generator charges the batteries.
A generator on board is only one part of a system. Its output has to reach the consumer unit through a changeover or transfer switch, be protected correctly, be earthed properly, and feed battery chargers that suit the batteries fitted. A fault anywhere in that chain looks, from the saloon, like the generator is not working.
We are clear about the split of work. Engine mechanical servicing such as oil, filters, impellers and belts is for a marine engineer or the manufacturer's dealer. We look after the electrics that connect the generator to the boat and diagnose electrical faults on the unit itself.
These are the complaints that most often bring us aboard:
An electrical check works through the whole path from generator to load. We inspect cable condition and terminations for heat and corrosion, confirm that protection is correctly rated, test the changeover so shore and generator supplies can never be connected together, and measure output under a realistic load rather than with everything switched off.
Earthing gets particular attention. The neutral-to-earth arrangement for a generator on a boat is different from that on shore power, and getting it wrong can leave RCDs unable to protect you. We also check the start battery and its charging, since a generator that will not crank is often simply a neglected battery.
Many owners now run the generator less, using a larger battery bank and an inverter for day-to-day loads, and starting the generator only for heavy demand or to recharge. That approach depends on a charger big enough to make good use of generator run time and, with lithium, a charging profile set for the batteries.
We supply and install Victron inverter-chargers, which can blend generator or shore power with battery power, and Fogstar LiFePO4 batteries. Our guide comparing a generator with a lithium bank sets out the trade-offs.
Generators suffer when they sit unused, and electrical connections suffer in the warm, damp compartment they live in. Running the unit under load periodically, keeping the start battery charged and having connections checked as part of winter or spring preparation all reduce the chance of a failure when you need it.
A generator produces mains voltage and can kill. Never work on its output wiring, the changeover or the consumer unit with the generator running or able to start automatically. Carbon monoxide is also a serious risk from any combustion engine on board; exhaust systems need to be sound and a working CO alarm fitted. If a generator or its wiring smells hot, shut it down and have it inspected.
No. Oil, filters, impellers and other mechanical servicing are for a marine engineer or dealer. We handle the electrical side and electrical fault finding.
Common causes include the generator's neutral-earth arrangement, a fault on a circuit that only shows on generator supply, or a changeover problem. It needs testing rather than guessing.
Often, yes. A larger battery bank with an inverter-charger can cover daily loads, with the generator used for heavy demand and recharging.
Yes. See our marine generator installation page for how we plan and fit a new unit.
Tell us the make, what happens and when, and we will plan the right check.