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Old 10-24-2019, 12:34 PM   #201
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Cummins rating definitions can be found here: https://www.sbmar.com/technical-info...s-definitions/

So for your engine rated at 2800, cruise RPM would be 2600 or less according to Cummins.
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Old 10-24-2019, 12:47 PM   #202
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Perfect, thank you.

So besides massive fuel bills, are you giving up engine life if you run regularly around 2600? I feel like the answer should be no, based on the rating, but that contradicts a lot of what I read here. Like if you knew that the PO ran the boat like that, you should run fast and far.

Just trying to understand what is real vs lore here.

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Old 10-24-2019, 12:57 PM   #203
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Excluding very low loads where there may be under-loading issues on some engines, yes, running it harder will give it a shorter life. However, up to a certain level of output, it'll be able to provide that and still live a long, happy life.
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Old 10-24-2019, 01:14 PM   #204
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Quote:
Originally Posted by BDofMSP View Post
Perfect, thank you.

So besides massive fuel bills, are you giving up engine life if you run regularly around 2600? I feel like the answer should be no, based on the rating, but that contradicts a lot of what I read here. Like if you knew that the PO ran the boat like that, you should run fast and far.

Just trying to understand what is real vs lore here.

Thanks,
BD
No.
Long engine life has to do w a lot of variables. But rpm run has little to do w it and usually running a higher rpm is almost always accompanied by lower loads and almost always lower tempetures as well.

The wear on the cylinder walls and pistons is IMO a direct result of sideways forces transferred from combustion forces w the offset crankpin. So a little less pitch, or lower gear ratio resulting in more rpm will result in extended piston, piston ring and cylinder life.

Many disagree w me on this. I remember Marin Faure who said engine life is a result of how many times the piston rises and falls. Simplistic idea I think. Wear needs to be related to work done that is directly related to piston forces.

So I think engine load is the dominant controlling factor regarding engine wear. Not rpm.
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