Engine/Transmission (1994 - 1998) Dodge 12v Cummins Installed in Boat

[fishjack1]

*I may have should have put this post in the "General Diesel Topics" not sure?



A gentleman I met this weekend while fishing has a boat with (1) Cummins 12v Marine diesel and he just installed a 12v out of a 1994 Dodge. Obviously the Dodge stock unit is lacking in power compared to the Marine 12v. I told him I would help him get some more power out of the truck motor and wanted some suggestions.



The 1st thing I was going to suggest was a TST power kit. I am going to pull the plate out of the marine engine to see how it is cut. I figure this would be a good start. Maybe some 370 injectors? Not sure what rating the marine engine is but will check when I go to visit the boat next week.



Any suggestions welcome. By the way this guy hauls waste oil for a living and runs (3) Dodge Cummins trucks. Got to get him on the TDR.



He also told me he has 3 more used Cummins 12v engines out of dodge pickups laying around his shop. :--)

 

[Forrest Nearing]

man, just cut that plate flat and deep!

 

[fishjack1]

Yep Forrest - That was my 1st thought but I hate to have the ole Dodge Cummins out power that stock Cummins Marine 6BT :-laf

 

[Vaughn MacKenzie]

I don't know what sort of duty cycle and load your friend expects to put on his "replacement" engine, but the Marine versions are built with higher sustained loads in mind. Cranking a 160hp version to 300+ HP then running it at 80% or more power for long lengths of time might be asking for trouble. But it might do just fine. . . just watch those EGTs. One thing for sure, I would not run 370s because of the non-ideal spray pattern. Go with something that matches the stock piston bowl.



Vaughn

 

[fishjack1]

Thanks Vaughn - That is exactly what I told him as my "disclaimer" that the Marine 6BT is designed to run at higher "sustained" loads.



I don't think most marine diesels have egt gauges but I will insist that he install one on the motors after we make any mods.



I agree the 370s might be a bit extreme and I told him about the spray pattern and piston bowl differences.



I still figure that a TST kit (or individually source a new/different fuel plate with an adjustable boost elbow) is in order. ?. ?

 

[JGK]

I heard a comment once by an informed member of this group that there is also a difference in the cam. The discussion was the differences between the PDR cam and the DD cam (I think that was the other one). The comment was that the latter (DD?) uses marine cams because the gear is held on to the cam shaft by a long bolt, whereas cams out of our land-based truck just have the gear pressed on.



The reason for the bolted gear is that in the marine application, where power levels are like 80% for extended periods, as mentioned, the street versions tend to break the shaft The bolt in the marine version is inherently stronger. Don't know if any of it is true, but the person telling me this is reputable.



In any case, the point is, the marine version is set up for a different application and a street engine in a marine application may not last!



FWIW,

-Jay

 

[BTighe]

yeah what they said, tst doesnt recomend this upgrade for engines that see a full load for 50% or higher. it went something like that, cant find the papers right now. its his boat so if thats what he wants do it .

 

[JLEONARD]

I would make sure you have a pyro installed... if he has a marine exhaust manifold that means a post turbo installation.

From reading marine forums I think 900 F is about where you want to max out.

I would suggest going into www.boatdiesel.com and browsing the Cummins forums. These guys don't do much bombing, but it's a good source for info.

BTW, that engine needs to be able to hit 2600+ at WOT with a full load. Cummins marine specs say if you can do that you can run continuously at 2400.

Make sure there is plenty of cooling water available as these engines are a little sensitive in that regard. But feed em enough and they'll run a long time.

Hope this helps.

Jay

 

[pwerwagn]

I have heard the same.

I've also seen a "dissected" marine cam that shows how deep the bolt is.

 

[fishjack1]

Thanks for all the input guys... I am going to go take a look at the boat and engines next week. . I will get more details on his setup and report back.



Like BTighe said "its his boat so if thats what he wants do it". I'll just make sure he understands the differences and the possible consequences.

 

[RChamberlain]

is he looking to sell those engines if so how much and are they good ones

 

[fishjack1]

RChamberlain - not sure what year the engines are that he has "laying around". But I am going to find out. . Hope one is a '98 12v that I can talk him out of

 

[JLEONARD]

I've read in a few places that the truck engines are ok in marine use provided you keep them in the 250 hp range or less... much over that and the duty cycle will kill them.

So if it were me that's about where I'd start and use a pyro to monitor.

So perhaps that's a good place for your friend to start figuring his prop size from. Then build on that based on what the pyrometer says.

FWIW that would be my approach.

Jay