I have a 23' deep-v thats about 35 years old. Currently, it houses a GM 454, that is original. It has a lot of hours on it and has been in storage for about 8 years. Last summer, we fired it up and water made it into the engine. Figuring that we will not repair the 454 that it has now, I was considering the possibility of replacing it with a duramax. Has anybody done this or know of anyone who has. If anyone knows anything about the ease/dificulty of this conversion or anyone who has thoughts on advantages/disadvantages, please post. I am interested in hearing all angles before i make any concrete decisions.

 

no

 

I've never heard of a dmax marine engine. I know cummins has one but thats a lot of heavy motor for that size boat. Most people I know who swap out gas for diesel use Yanmar diesels. There suposed to be really good marine engines. We have a yanmar diesel tractor and if that can be any judge its great. Almost 20 years old and looks/runs like its brand new.

 

the boat, as it sits, weighs around 9700lbs empty, so i dont see where it would care about something the size of a duramax compared to the 454, but the marine build is one of my main concerns. Is a dmax enough stronger to begin with that it would be able to survive in a marine useage?

I have also been looking at yanmar as well, and that is still a possibility. (anothere 454 isnt out of the question either, I just wanted to do something a little different)

 

You could try mercruiser or volvo penta's diesels. I think cummins helps make diesel engines for mercruiser.

 

Cummins and Mercrusier have a series of engines and drives out the engines are mad by VM.Not cheap but you would get your money back in fuel saving after a couple of years

 

How bout a built and blown 502?

 

The real question is what drive are you mateing the new engine to? Your ability to even bolt up will be nearly impossible. Will your drive handle it? doubtful, especially if its a Merc/ and or 35 years old. Next problem is exhaust manifolds. You will need water cooled- availabilty is doubtful. Motor mounts? Also doubtfull. Next problem is the electronics must be stand alone. Throttle control, gauges, and alarms will have to be overcome. Bottom line- Dont do it. Cummins and Yanmar both have arrangements with Merc. Many have been left scratching over who to take their boat to for service. The Merc drives have always been a weak link. Volvo makes their entire package. The Swedish drive has no equal. They invented the Duo-prop 14 years ago- Merc is still trying with their Bravo 3. Footprints on the Volvo's are designed to drop in where a SB or BB once was. I have installed and run both their electronic and mechanical engines. With an addition of the supercharger on a turbo'd and aftercooled engine- it behaves just like a gasser. The electronics on these engines is nothing new. Taken from the their truck and construction cousins over a dozen years ago- it is perfected. Dont let anyone tell you it doesnt hold up in the marine enviroment. Their model 300 (285 hp) will cut your fuel burn more than half, and run just as fast as your 330ish @ 4400rpm BB. The newly introduced D-6 (310 or 370 hp respectivley) will flat out smoke (no pun) your gasser. Good Luck--

 

How many hours is alot? More than 5000? More than 8000? Considering that a DMax isn't made for marine usage, you're doing an uphill battle. It needs to be converted to marine use. That costs money.

I remember when I replaced the two-stroke oil guzzling DD's from my boats and replaced them with marinized Cummins engines, I had more space left over than I thought I would. So, I used the extra space to put in an Onan 6.5 genset. That was a smart move, on my part.

Getting back to your question. It's cost prohibitive to do it with a boat under 30ft. I'd just repair the 454 and use it until you can't buy parts for it anymore.

 

572 GM crate

 

I'll compromise with ya. A built and blown 572.

 

Looks like dmax isnt a good idea..... they are expensive anyway..... cummins would be nice, but too large and heavy for what they are..... (good for tow vehicle ) the 454 that is in it is toast.... its time for a new engine. some of the parts are usable (starter, alternator, hydraulic pump, etc) but the block is cracked in at least 2 places, the exhaust manifolds and cooling system is almost completely plugged up with rust.... that in mind, i am looking for a new crate motor and a new sterndrive to match unless i get another 454 that will match up correctly.... a 572 really would be fun..... any ideas on cost for the 572 plus sterndrive? or a new 454?

 

ok time to learn, what are the diffrences between marine and non marine engines?

 

Whatever you go with make sure its built for a marine application. A reg car gasser wont last long. A boat engine is designed and built to work at full load 100% of the time. IMHO you wont go wrong spending the extra money on the diesel Yanmar/Volvo setup plus you will probably get most back on resale. Like your truck once you go oil in a boat you wont go back to gas

 

If you want to go diesel, why not go back to the old 6.2L GM diesel? I seem to recall hearing that they had a marine version available and though they were no powerhouse on the road, they were reasonably reliable as a highway cruising motor in a 1/2 ton pickup.