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Diesel overload article vs. Nordic policy?

Diesel overload article vs. Nordic policy?

Postby Ben McCafferty » Wed Sep 20, 2017 8:31 am

Hey all,
Just read a good article I had found http://mvdirona.com/TechnicalArticles/DieselEngineOverload/AvoidingDieselEngineOverload.htm on diesel overload; it is written by James and Jennifer Hamilton and refers to advice from Tony Athens. It essentially says that many manufacturers (over)prop their boats when new for maximum speed (for marketing purposes), based on the original weight and little fuel/water/etc.

It occurs to me that Nordic Tugs is more or less obsessive about their build quality and reliability. Since they are not a "go fast" boat, I'm curious what your experiences have been regarding this over-propping question. In other words, have they propped correctly up front, at the expense of a little top speed, to give their boats maximum life and reliability? Or have they fallen to competitive pressures, needing to say that their "fast trawler" can do 17 knots or whatever?

I'm really curious to hear your experiences, especially pertaining to how your tugs have performed when loaded and when the bottom is fouled. Have you still been able to hit max rated RPM? Have you needed to prop down? Any early failures or problems due to overloading?

Thanks for the collective wisdom, talk soon.
Ben McCafferty
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Joined: Sat Sep 02, 2017 4:52 pm

Re: Diesel overload article vs. Nordic policy?

Postby Bill Stone » Wed Nov 22, 2017 2:29 pm

Sorry for the slow response. we have 42-110 with a five blade prop, Cummins QSC8.3. Max rpm rated at 2600. Since new we have consistently gotten a max of 2680 out of the engine/prop combo. I have been told that it is preferred to be slightly above the max rpm rating.
As such, in our case anyway, believe the boat is propped right where it should be.
rgs, bill
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Bill Stone
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Location: Anacortes, WA>

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