I always hear Diesel engines run for ever? Do they? I see a Dufour 43 for sale engine hours are at 3900 that sounds scary right?

4000 hours is a lot for a yacht engine but as I mentioned in the other post a lot of yacht owners do a lot of motoring these days. Most yacht motors fail from internal corrosion. They are not run often or for too short a period or with no load so that the condensation does not get a chance to burn off.
The Kubota auxillary in my fishing vessel when I sold her had done 17,000 hours. The Gardner main had no hour meter but has run long hours since 1945 and continues to do so now.

With regular changes of the correct coolant, if its a freshwater cooled motor and regular oil changes of the correct grade and classification oil, they should last a very long time. Avoid modern oils, the correct classification is important.

Toph said..

I wouldn't have a clue about your actual question southace, but for me personally, I would much rather a high time engine that has been maintained regularly, then a low timed engine that hasn't. Can they produce receipts?

That is what I think as well.

Diesel engines last longer if driven hard ie at their maximum continuous rated horse power RPM. This is usually their most economical speed as well.

If the engine is nursed at low RPM it will not attain it's correct operating temperature and the bore will become glazed, there will be blow by to the sump, the oil will become contaminated and wear will be accelerated. Further, the fuel control rack will wear into an area which will most likely prevent the rack from opening up to full fuel.

If you are driving a car at 100kmh and travel 100,000 klms that equals 1,000 hours of driving, therefore when thinking about engine hours on a boat 1,000 hours of running is equivalent to 100,000 klms on a cars odometer.

My Peterson 42 had a Nanni marinised 4cyl 43 HP Kubota in it. Probably the same engine as Ramona had as his auxiliary in his fishing boat.

I saw one of these engines on the bench at our local Kubota dealer's workshop. It had been a fishing boat's auxiliary engine and had 26,000 hours on it. That is three years running non stop except for shutting down for oil and filter changes and like a taxi, the engine never got dead cold.

The dealer only de-lipped the bores, reconditioned the valves, fitted new rings, bearings and gaskets and sold it to a farmer as an irrigation pump engine.

If you are looking at buying a yacht and the engine hours are low indicating it has been run for less than 100 hours per year for the age of the engine, be wary of it. Even though the oil might have been changed every 100 hours, it has been sitting in the engine deteriorating for a year building up acidity and moisture content.

If the yacht has an engine log separate from the nav log it is a fair bet it has been maintained correctly.

There are more marine diesels that die from under use than over use.