180hp cummins to 210 hp cummins

[michael semien]

Hi Tony
I have a 31 Bertram with 2 180hp cummins diesels that are old but run just great with no major issues. My top end speed is about 16 knots at max rpm on both engines. I am running 20 x 20 props behind twin disc 2:1 running gear. I heard from the local gallery change the props, change the gear, change the injector pump etc. I would like to keep these engines until they die. What can I do to increase the hp to at least 210hp and get more speed without straining these engines? At the end I will repower probably with cummins since I think they will fit the same existing footprint. My neighbor is a Yanmar man and swears by them but I think that that would be too much of a modify job. I will stick with CUMMINS.
Maholo from Hawaii
Capt. Mike

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[michael semien]

Thanks Tony

Excellent response. Would changing from these twin disc to 1.56 ZF 63a’s be almost seamless as far as size or would I need more modifications.

Thanks.
Capt. Mike

[Tony Athens]

Unless your 31 Bertram is a heavy tank, (like over 13,000 lbs) then a pair of good running 6BT 180’s should make real close to rated RPM ( 2500-2550) swinging 20×20 3B’s with 1.56 ZF 63A gears and give you over 20K’s..

Are you sure you are loading the engines to their full potential? Got accurate boost & RPM numbers?

Bottom condition? Quality of props and running gear ??

Bumping up to 210 @ 2600-2700 is doable, but at this point, something may be not as I would think..

Tony

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