converting a truck engine to marine

[skovian]

Hey Everybody,

If you were going to convert a truck engine to marine, which would it be: Cummins 6BT 12-valve or 24-valve, or GM 6.2 or 6.5 liter? And why? For fun, lets suppose this was going to be the only engine in a 10-meter boat.

Thanks for your opinions

[seapower]

I can't speak for the GM,s, but the Cummin's Marine engine is a marine engine, not a highway use engine. Beside's the bolt on "marine" part's there are difference's inside. True marine engine's are built for higher cylinder temp's and pressure's because of the increased load's they push. Think of it as this; highway vehicle's run down the road at what 1800, a marine engine is expected to turn 2600 to 3000 rpm with no over-drive and pushing that load uphill at all time's. Also by the time you add all the marine bolt on part's to your "truck" engine, I don't think you'll be saving any money, probably will cost you by the time your done. A short list; flywheel, flywheel housing, housing adapter plate, drive plate, engine hanger's, mount's, heat exchanger (if not keel cooled), after cooler, raw water pump, etc... Some commercial guy's did use truck engine's in their work boat's, for the most part they were slow turning, keel cooled engines. Just my opinion, but you asked. Frank

[Avenger]

Most marine engines are based on automotive or Ag/Industrial engines, but as seapower said just because they're based on them doesn't mean they're the same. You need to do a lot of homework to convert one.

That being said, in answer to your original question, I would avoid the GM 6.2/6.5. It has a bad reputation, largely deserved.

The B series Cummins OTOH has an excellent reputation and is more likely to be able to handle the job. I would suggest the 12V since all the 24V truck engines that I'm aware of are electronic, which does not lend itself to tinkering.

I would also suggest that if you plan to use this hypothetical boat offshore and your life depends on this one engine that you go buy a good new or rebuilt real marine engine.

[seapower]

Kinda what I was saying, I didn't want to come right out and slam the Detroit engine's. Some engine's live well in the automotive and construction world, but don't so hot in the marine side of thing's. Those are a good example, but there are many more. The idea of converting an automotive engine to marine is ok, for someone that has alot of time and money on his hands looking for something to tinker with. For cost effectiveness, it's a no go. Like I said the internal's are different to (valve's, cam duration, injector port size's, etc...)
I'm with you, when I'm offshore I'll take the sure thing everytime. Frank

[Avenger]

I'm with you 100% Frank. I can speak from firsthand experience with the GM 6.2/6.5L. I've owned four of them. Three in one truck alone.

Let's just say it ain't no Detroit.

[Questsportfishing]

lets see first off if you look at 'how' a marine engine is put together the parts list varies a bunch. mostly in bolts, nuts, plates, etc.. you take a 'steel bolt' that has no protection .. insert it in another 'dis-similar metal' in an area that has no zinc holders or zinc protection and you rot / canker / rust your engine out from the inside out.. or you can never get the bolt out again because it fuses itself to the block.. if you understand these things then your golden and you can change some things over .. but be careful the price goes up sometimes by far... 1 marine riser or cooler that may fit the marine app may not fit the truck plates.. stuff like that gets to be problems and time and money.. talk to your friends and ask them do you want to fish now or wait a year and a 1/2 while I build my engine??? hint even if you do convert one ... don't ask your wife..!