Understanding engine hours of a Boat!

Yachtbroker’s view.

This is my attempt to put some understanding of the meaning of engine hours: As such they might not mean much they are only a number or indication not a substitute of the condition of the engine. They could be accurate and might be understated, e.g. if the hour meter was out of action. In any case they cannot tell you the complete story of the engine’s condition. I am writing this as a yacht broker rather than an engineer.

We are told that engine hours are something like 5 to 10 times as stressful as the hours on a car or lorry. The main reason for this difference between a vehicle and a vessel is that there is no clutch. All of the stress of throwing the engine into gear and the propeller and shaft turning in the water without a clutch, means that this direct effort required considerably increases the wear and tear on the engine.

Engines can be used; lightly on the river,  in a heavy sea, at tickover in neutral, these situations are all very different and as such engine hours do not reflect the actual condition of the engine. Engines like to run long and steady. The longer the running time between stops, and the shorter the idle time between runs, the longer the hours they will deliver before needing major repairs.

100-200 hours per annum is an average for a boat. Larger boats can have higher averages, a Superyacht can go across seas and can have an average of 500 hours per annum. They have bigger engines and are better able to manage these. Most engines are detuned lorry or car engines. Petrol Engines are less able to manage this stress and need up to three times the maintenance of a marine diesel engine.

As an example let us take a car diesel engine, 250,000 to 500,000 miles are normal expectancies between major services for a good one that has been well maintained. At 30 miles per hour average this would be 8,333 to 16,666 hours this would be a lot of hours for a boat.

A boat’s engine would normally need to be the subject of a major overhaul and replacement of the major engine components after 10  years at 100 per annum that is 1000 to 2000 average engine hours. At 22 knots that is 25 miles an hour and approximately equivalent to 25,000 miles – for a boat and 250,000 miles for a vehicle neatly fitting the estimate of  5 to 10 times the wear.

A footnote these are only approximate  guides and a well used and well maintained (and well documented) boat is better than one which has low engine hours but no maintenance.

Prospective clients will can always ask for the engine hours at www.coastal-leisure.com

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