Are powerful diesel engines damaged by low speed inland use?

Montemar

Montemar

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My scenario is the continuous use of a diesel engine of the power needed to get a sea going boat on the plane being used on inland waterways at low speeds. I would expect the engine to get coked up because of low speed gas flow through the valves and cylinders. However I get the impression that more damage than that is caused resulting in major repair bills. A decoke may not be easy but could be done without removing the engine.
Any information on this would be greatly appreciated.
 
Your intended use requires more explanation really, however if the inland use is only temporary don't worry about it, on the other hand if it will be permanent then you probably have the wrong boat and need to look to change.
 
I ran my last boat in this way for 6 years and (600 hours) with no issues. It would occasionally feel a little choked but a good blast would sort it out. On longer holiday trips we do get to go fast but that is a small number of hours.
There are hundreds of boats in the marinas here which are used in the same way.
Some engines are more tolerant than others. What engines do you have in mind.
 
In the grand scheme of things our KAD32 isn't a massive engine however you can still tell when it has had enough of pottering around on the river. It gets coked up and starts to smoke which signifies its time to take it out for a good long high speed run. We are fortunate where we are based that although inland we have plenty of waters in close proximity where we can open the boat up and give her a good clear out when the need arises. If we didn't have that option well we wouldn't have this boat, there are far better suited boats and engines for inland cruising.
 
There are 100's of overpowered boats trundling up and down the Thames and after 40 years of this I haven't heard of any requiring major rebuilds due to pottering slowly on the
river. Usual problem is when taken down to the sea is sludge in the fuel tanks gets stirred up and blocks the filters, some older 60's, 70's technology engines seem to suffer a bit and
make a lot of smoke but generaly I think your statement is a myth perpetuated by internet forums.
 
As Chris said, this was more of an issue with older engines. My first boat had a pair of Perkins 6354's and I had the turbos rebuilt a couple of times as they hated slow running. Modern engines are far more accommodating but the stories are perpetuated to cover the bums of manufacturers/service companies just in case.
 
Wavey said:
As Chris said, this was more of an issue with older engines. My first boat had a pair of Perkins 6354's and I had the turbos rebuilt a couple of times as they hated slow running. Modern engines are far more accommodating but the stories are perpetuated to cover the bums of manufacturers/service companies just in case.
Click to expand...

Unless you have D3!

In which case the variable vain turbo will take instant dislike to river speeds, coke up and render itself useless in next to no time at all.
 
...or a KAD44 / KAD300 where the top end disintegrates under prolonged low load conditions unless you make a mod to increase oil flow.
 
Our last boat had kad300 s , I heard that at low speeds the last cylinders starve of oil due to the rise of the bow at low ish speeds, don't know if this is of any use, however I always felt they wanted to go at higher revs than low revs, we are on the coast so was never a problem. Just one thing to mention if you are going for a boat with kad 300 check the tappits adjustments and when they were last done, another thing I learnt from this forum��
 
I have heard of the KAD44/300 oil starvation issue too from no other than Volvopaul but I also know owners of a F37 a T37 and a Nimbus with KAD44s that have done 100s of hours on the river with no issues, also a D9 engined boat that has similarly done hundreds of hours with no issues. As for D3's I would never buy an early One because the of the variable vane turbos which give problems regardless of where they are used.
I Agree with Wavey there are loads of old Perkins 6354s on the Thames belching smoke and perpetuating the myth but that's more to do with them being 40 years old and designed 50 years ago. Honestly this issue is massively overstated and is only likely to be a very long term issue after 1000's of hours if at all.
 
A engine needs to be worked hard sometimes to keep the rings/bores happy, this is the same with ALL diesel engines. fitting a small prop will just annoy it.
Constant low speed will coke up the turbo till it no longer works, you can remove the turbo and a good engineer can de-rate the pump in such a manner that it could be re-fitted at a later date without problems.
Use a good additive such as Re-vite and give it a good blast when you can and it should be fine.
 
some years ago I bought a boat which had spent 7 years (since new) on the Upper Thames. I had it trucked to the south coast and was concerned about how the pair of perkins sabre 225Ti's would shape up when opened up for the first time in their lives. There were no issues whatsoever and they both ran sweet as a nut for the next 7 years
 
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