What engine hours really tell you

Engine hours are to a boat what mileage is to a car — but the story is more nuanced for marine engines. 100–200 hours a year is normal use for a cruising boat. On a ten-year-old boat, 1,500 hours is a healthy figure; 150 hours on the same boat is very often a warning sign.

Why an under-used engine is a risk

Diesel engines are designed to run. In engines that sit idle for long periods, seals dry out, injectors clog and corrosion advances in the cooling circuits. An engine running 15 hours a year can cause more trouble than one running 150.

Read hours in context

Hours should never be judged alone but alongside three things: the boat's age, its service records and when the last major service (injectors, turbos, cooling) was carried out. A MAN engine with 3,000 hours serviced every 250 is far more dependable than an unserviced engine with 800.

That is why the engine-hours filter on Yacht44 exists — not to reward 'low hours' but to help you find a genuine usage profile. When in doubt, request an oil analysis; for a few hundred euros you learn the true internal health of the engine.

Life expectancy by engine type

Slow-revving heavy diesels (MAN, MTU, the large CAT blocks) run 10,000–20,000 hours with proper care; light high-revving diesels (Volvo Penta, Yanmar, small Cummins) come up for major overhaul around 4,000–6,000 hours. Petrol engines last far less. The same '1,500 hours' means 'young' for an MTU and 'old' for a small petrol engine — read the number against the engine's class.

Oil analysis and the sea trial

An oil analysis measures metal particles, fuel dilution and coolant ingress in a sample of engine oil; for 100–200 euros it tells you about internal wear the surveyor cannot see. On the sea trial, note whether the engines reach the manufacturer's rated rpm at full throttle, the exhaust colour and the temperatures — an engine that cannot reach its rpm is the first sign of a propeller or injector problem.

Using the engine filters on Yacht44

In the ENGINE DETAILS filter on the boats-for-sale page you can set a minimum for engine hours: on boats over ten years old, 'at least 500 hours' filters out engines that have sat idle. Read the engine-make filter together with age and hours; the comparison tool shows engine hours side by side and flags the lowest — but as you now know, lowest is not always best.