Up-Rating info, Cummins


Sep 8, 2012
Huntington, NY
Hi all,
I really enjoy reading about the wealth of information and insight on these forums.
Can anyone tell me the approximate cost involved to up-rate a 2002 Cummins 6bta from 330 up to 370 HP? Also would it be safe to do so on this year engine with 1700 hrs on her?


Sep 1, 2011
Portsmouth NH.. Piscataqua and Merrimack Rivers
Boat Make
27 H&H with Cummins QSB 5.9 480 power
Maybe this will help answer your question.

A question was asked on boat diesel similar to yours by "CaptChuck" and answered by Tony Athens who knows his stuff about the 6BTA 330 and 370.

Power uprating advice and info:

"I could use some advice regarding a HP boost to a 2002 cummins 6bta-330 with 1650 hrs. I´m interested in DE that has this motor with a reported cruise of 13.5 knots at 2400 burning 10.1 gph. She is apparently propped correctly for a wot at 2803 pushing her max at 16 knots. I would like to get a little more cruise speed (15-16 knots) and was wondering if you could give me some insight into possibly doing a 370 hp rating increase on the motor. Would it be risky to do this to a motor with 1650 hrs.? What realistic speed increase could be expected on the full displacement DE 16,000 lb hull? Would a re-prop be likely? What would it cost to do this sort of upgrade?
It seems like the Cummins specs indicate a similar fuel consumption while gaining 30-40 hp at cruise."

Thanks All!

Tony answered:

"In general, the safe cruise HP available from either engine is close to the same .. As to the graphs, you are reading them wrong.. You DO CANNOT extract or deliver horsepower from the engine without using more fuel."

Apples for apples---------

330B = 315 BHP at 2800 MINIMUM RPM, but do much better as to performance when they are propped to 2925-2950

370B = 355 BHP at 3000 MINIMUM RPM, but perform way better if propped to 3125-3150

Net hp GAIN IS 40 bhp, but only if the engine can make 3000 ++ rpm.

In most cases on a boat like you describe, you would prop down 1" of pitch minimum in order to use the small amount of extra HP.

IMO, it´s not worth it.. If you are not fast enough, remove 2000-4000 lbs of weight, or get a new higher HP engine.


Thanks Tony. I understand what you mean about the fuel burn/HP relationship. I may just look for another boat. Don´t want to invest an additional 50K on top of the asking price. If I could get by with only 2-4k to safely get a couple more cruise knots, I thought it may be an option to consider.

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