"What are the real differences between the 6BTA 315/330 & the 6BTA 5.9 355/370 D

[Frank Masseria]

I run a 27 foot H&H Osmond Down East boat as a 6 man charter boat. The boat is powered with a 2001 330hp Cummins 6bta Diamond Series engine. CPL1975

The engine has just about 5400 hours on it. Overall it runs well. Max rpm are 2800 at start of season but seems to drop off to around 2700 mid season which I attribute to some growth and slime. The boat is kept in New Jersey. The propeller is a diameter of 23″ and a pitch of 21″. Fully loaded I average honestly 13-15 knots at 2200 rpm depending on current and wind.

Im looking to try and get  to cruise at 17 knots and was considering having my engine retuned to create 370 hp. The thought being the 40hp would enable the extra 2 knots Im looking for.

From what I read my Bosch P7100 pump would need recalibration. Not sure if my injectors need to be changed and if any valve adjustments are required.

Looking for any feedback. Is this a sensible thing to do. Im brand new to the site. I read Tony’s article on Propellers Move Boats.

Any feedback much appreciated.

Topic

[Tony Athens]

Frank,

 

You will need to have your pump re-calibrated to a either a CPL 2208 or CPL8457 Spec and get new injectors for which ever CPL the shop can calibrate it to.

 

This is GOSPEL–Once you do this you will need to remove at least 2″ if not 3″ of pitch as now the engine will need to spin up to  (accurate) OVER 3100 RPM and do it easy.. The extra HP ( from 315 to 355) is there,  BUT ONLY above 2800 RPM.  If you do not follow my advise, you’ll be on a road to even an earlier death for your engine..

 

Tony

[Frank Masseria]

Thank you Rob for your reply. No doubt I have to have my prop reworked. Rechecked my RPMs after reading your reply. With full fuel tanks and one other person on board I was able to turn 2775rpms. Need another inch or so of pitch taken out but if I did the upgrade I would purchase a new prop configured correctly. The extra horse power is very important to me because of the weight I carry when chartering. I know she has 5400 hours on her but she honestly runs well and I would be willing to take the gamble of the upgrade.

My question is do I have to bring the pump to Cummins for recalibration. How can I determine what injectors I would need? I would be looking to do the on boat work of removing pump and injectors my self as well as replacing the new equipment.

From what I read its really a recalibration of the Bosch p7100 pump and new injectors. I know if its not broke don’t fix it but in this case I am willing to make the exception.

Thank again

[Rob Schepis]

Already Working Too Hard..

Other than inj pump fuel delivery specs the two engines are the same.  I’m just not 100% sure on injectors..

Propped correctly, at the same cruise speed you’ll be burning the same fuel but yes the 370 can make your boat faster when you want/need it too…But pulling that extra HP from the same engine (when you are going faster than what the 330 gave you) will come at some cost of engine life and it sounds like you want that extra HP most of the time..  IMO it might be a “big ask” of a 5,400hr engine that is already working too hard (quite over-propped as a 330 should see 2900-2950 easily)

Normally you’d have to prop back an inch or so in pitch from a 330 to a 370 but in your case sounds more like 3″ since you’re already over-propped.  On a positive note lower pitch could add a benefit of slower boat speed at idle when maneuvering in close quarters.

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