Originally Posted by manyboats
Marin what do you think is going to break or get damaged when you run WOT?
Or when you cruise at 2100 rpm?
what is going to have its life shortened if an FL120 is run at full throttle or power settings much over 2000 rpm for longer periods of time because a fellow who got real rich in the UK overhauling them told me.
The injection pump.
According to him it is the single weakest link on the engine and is one reason the Dorset engine proved to be such a miserable failure as a truck engine. Other components of the engine are less-than-ideal, too, but the pump was--- under high rpm, constantly changing high-ish loads which is what you have in an over-the-road truck--- very prone to either outright failure or rapidly deteriorating performance. Our acquaintance told me that overhauling the Minemec/Simms/Cav in-line pump on the Dorset engine back in the day let him pay cash for a new Rolls Royce.
Ironically that same pump did just fine under lighter and more constant loads which is why the Dorset engine proved very good in its day as an industrial and agricultural engine. And as a marinized engine in boats.
The Dorset engine is also very susceptible to heat damage. In fact, our friend said overheating is the number one killer of the Dorset engine. Not that it is prone to overheating but if something happens with the cooling system and the engine is not shut down before an overheat occurs Bad Things happen fast. The head gasket is apparently looking for any excuse to blow and the head itself will warp quite happily.
We met this fellow initially in Ganges on Saltspring Island where he was cruising in his sailboat which had---- an FL120 in it. He asked us what kind of engines we had and that's what got the conversation going. He had not only owned one of the biggest Ford of England diesel repair and overhaul shops in England but he said that for many years he'd been a consultant to Ford of England on their diesel engine programs. The voice of real-world operations, as he phrased it.
The Dorset, he said, was not a bad engine given the era in which it was designed. But it was designed at a time when trucks were rapidly getting larger and heavier and road speeds were going up. The engine would have been great in the 1940s. But it simply wasn't up to the job that was being asked of it.
In a boat, he said, it's a great engine. But only if you run them under the loads and rpm at which it experiences it's longest, most reliable life. The best rpm band, he said, is 1500-1800. And never, ever, EVER, he cautioned me several times, let them overheat. If I think one might be, he said, shut it down as soon as you think that. Don't wait to see if the problem is really happening, or will get worse. Because if it does get worse by the time you realize it the damage can already have been done.
Now I've heard much of this from other sources in the marine diesel industry over the years, and I'd read about the Dorset's failure as a truck engine before I met this guy. But he'd built a business on dealing with this and many other Ford of England (and Perkins, etc.) diesels. So I give him a lot of credibility.
In my book, reality and first hand experience trump theory every time. So while someone like Steve D'Antonio may arise from his armchair and preach about 75 percent power loads all the time, every time or whatever, I'm going to listen to the British guy who bought a Rolls Royce for cash on the money he made fixing, overhauling, and living with the kind of engines that are in our boat.