Engines and generators

What to inspect · Power & sail

On most trawlers and cruisers the engines are the costliest single item. Watch a true cold start, read the service records, and hire a mechanic who knows that make for an engine survey with oil analysis. A general surveyor checks that engines run, not their inner health.

The cold start and the smoke

• Ask that the engines not be run for about a day before the survey so you see a real cold start. Stand where you can watch the exhaust as each engine fires.
• Blue smoke usually means oil is burning, from worn valve seals or, worse, worn rings. White smoke can mean water or coolant getting in, for example through a rotted exhaust mixing elbow or a failing head gasket. Gray or black smoke points to poor burning, such as bad injectors or a clogged air filter.
• A well-kept diesel, even an old one, should show little smoke. A marine mechanic writing in 48 North warns against anyone who says heavy smoke is just normal for an older engine.

Hours, records and age

• BoatUS notes that hours, service history and condition say more about an engine than its age. Ask for logs and receipts: oil changes, valve adjustments, injector service, heat exchanger cleaning and any overhaul.
• Read the engine room. Rust and junk lying about suggest an owner who rarely went down there; clean, well-kept machinery suggests regular care.
• The 20,000 hours before a major overhaul often quoted for a well-kept Ford Lehman comes from a former executive of the company that sold that engine. Treat it as a best case, not a promise.

Engine survey and oil analysis

• Hire a mechanic trained on that make for a separate engine survey on survey day. It can include compression tests, temperatures and pressures under load, and a look at mounts, cooling and exhaust.
• Take oil samples from each engine, each gearbox and the generator after they have worked on the sea trial. Oil with no hours on it tells the lab almost nothing.
• The lab looks for wear metals, fuel, water and coolant. Salt water or coolant in the oil points to serious internal trouble. Wear-metal numbers are easiest to judge against earlier samples from the same engine.
• BoatUS notes many larger engines built since about 2006 have computers that a trained mechanic can read with the right equipment; older mechanical engines don't.

Generator and the raw-water side

• Run the generator under a real load, not just at idle. A winterized generator may not be testable on survey day; agree in writing how it will be proven or priced.
• On inboards, look closely at exhaust risers, manifolds and mixing elbows, heat exchangers and raw-water pumps. A failure can let water into the engine. Replacing these parts is a normal cost of owning an older boat.
• Even if you plan to keep the old engines, BoatUS suggests getting a repower quote so the cost doesn't catch you by surprise later.

General guidance for recreational boaters, researched from the sources listed and written in our own words. Your equipment manuals, local knowledge, the Navigation Rules and a qualified instructor come first.