Automotive 6BT to Marine

[Alex Dubinin]

Hello everyone,
I’m building 54′ sailing boat, 90’000 lbs displacement.
“Voyager 542” – Bruce Roberts design
According to the project this boat requires max170 HP engine.

Due to restricted budget (to much expences in short period of time)
I bought Cummins 6BTAA-5.9
215HP/2600RPM from Dodge Ram 2500(1996 year built)
engine serial number 45262906,
fuel pump: in-line BOSCH P7100
engine configuration D403029BX02,
CPL:2023
During rebuilt it became clear that engine block requires re-bore and new oversize pistons, and now questions:
1. If I buy marine pistons but leave original camshaft and injectors (new nozzles) as they are in good condition – will I get some improvement or just misbalance whole system ?
2. Due to less HP required I would like to get rid from intercooler, is it possible and if so how many HP will remain?
3. This engine has HOLSET HX35W turbo is any possibility to marry dry turbo to wet exhaust manifold ?
4. Is any other critical differences between automotive and marine versions of 6BT except pistons, injectors and camshafts, which can prevent marine use ?
(Wet Exhaust Manifold, Header Tank, Primary Heat Exchanger, Raw water pump, Exhaust injection elbow will be added later when re-buit will be completed)

Your thoughts and experience will be much appreciated.

Thank you

Topic

[Tony Athens]

Keep us in the loop with pics and updates as you work thru the conversion..

Curious—-Why would a Dodge/Cummins engine be wore out unless we are talking 500,000++++ miles or something along those lines………………….. Avg load is 50-70HP with some WOT show-offs in the middle, and they just do not wear out unless ?????

[Alex Dubinin]

Your post and mentioned articles forced me to get dipper in propeller theory it took awhile and now picture become much more clear.
Many thanks for your kind assistance.
PS I found an example how to connect dry turbo to wet exhaust manifold

[Tony Athens]

Yes you are wrong………………….But before I do it here, absorb these two articles.. Then look at the prop curve below that would be very close to how this engine would load if propped per my recommendation.

https://www.sbmar.com/featured-article/continuous-duty-a-different-perspective/

https://www.sbmar.com/featured-article/propellers-move-boats-engines-just-turn-them/

Tony

[Alex Dubinin]

Dear Tony, many thanks for your reply.
Understood that idea of swapping to marine pistons is complete nonsense.
Regarding engine cooling and wet exhaust everything clear, thanks to your very informative and detailed website, my boat will have HX cooling and wet exhaust, importance of the high of dry part understood as well.
Just one more dark area, prop calculation, if the boat requires 170HP to sail with max waterline speed, why to use engine rated power for prop calculation. This extra power will considerably increase fuel consumption with no effect on speed. More over for cruise speed will be necessary only 120HP, that means most of the time propeller will run in inefficient range, or I’m wrong? as with marine pistons 🙂

[Tony Athens]

1) Buy over sized pistons specific to your engine serial number. If not available, then sleeve the block and use standard sized pistons.. ” Cummins call them “Sleeve Kit” for these lower HP engines.. Use a machine shop with long term experience with this engine. Or buy a GENUINE short block

2) Control the total available HP thru prop selection……..Prop for 200 BHP at 2700-2800 RPM. Use a displacement prop calculator.. The rest will take care of itself .

3) NO aftercooler needed but you must use a wet manifold

4) All the internal parts you use need to be for your engine serial number. Don’t dwell on “marine parts” for the rebuild part.

5) Plumb the engines coolant side per an off the shelf 6BT210–post 1995 plumbing.

6) Dry turbo adaptation–If you are very clever, maybe..

7) Think about HEIGHT so you can build a save exhaust.. That is the down fall of most sailboat home builds that use a wet exhaust system..Got some drawing ?

Look thru the pics attached–Try and glean what you can.. Are you going HX cooling or keel cooling? Wet of dry exhaust? Those are major engineering choices & you need a clear plan.

Tony

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