With the cost of gas looming at the $3.00 mark here in Detroit. I started thinking about repowering my boat (38 Scarab) with diesels. I was watching "Trucks" TV over the weekend and they had a feature where they were making biodiesel. I have always heard and know about this stuff for possible use in the truck but that was as far as it went. They were saying that you could make biodiesel for as low as
$.70/ gallon. I could justify repowering to diesel for fuel prices that low compared to $3.00+/ gallon for gasoline. Has anybody thought about this too? What kind of motors were you looking at.

I looked at a BBC to Yanmar conversion when I repowered 3 years ago. At that time the $$$ just didn't wash. Also looked at a GM P/U diesel and the accesories weren't there yet. Somebody is doing a marine conversion of the Hummer diesel but even now the price isn't justifieble.

I was told by GM engineer that they couldn't meet needs for Duramax for trucks so even looking at marine version or lower price wasn't worthwhile.

The Yanmar option is well engineered and you can buy complete package with rated outdrives or just the diesel to repower.

A Yanmar/Konrad kit would be a great option now. Wonder if Konrad has got the prelims done since they talk about some boats they've with diesels.

Somebody in in IN has a coversion using the 7.3 Internationals to repower boats with BBC power.

Chris

Looking at the duramax specs, they are rated at 310 hp and 605 ft/lbs of torque. How does this affect the sped of the boat. I assume the top speed is slower since the diesel cant spin as fast, but what about cruise speed and time to get on plane? I assume getting on plane would be DRAMATICALLY different since something like the duramax makes it torque peak at 1600 RPM.

These are a direct replacement for a BBC.
http://marinedieselusa.com/

volvo makes packages with drives up to 350 hp. about 400 pounds heavier than the 8.1 package. these come with a warrantee for the whole package & dockside warrantee service. they are also very fuel efficient. top end speed with the diesel is sometimes short of a big gas engine, but the cruise speed is usually much better as you can run them at almost full throttle forever.

I actually put a Duramax in my boat last year just to see how it would work. It pushed through an overbuilt B/W 72C to a SSMIII that I put 1.125:1 gears in. After defeating all the of the security system stuff and becoming somewhat of an expert in automotive electronics, I got it running. My gearing and prop selection was spot on, thanks to the coding behind www.speedboatperformance.com, and I ran 55 mph with it.

The torque curve of the Duramax was pretty cool in the boat. It would yank itself out of the hole, even with the 1.125:1 gears and a 29" pitch cleaver. I didn't use a big enough intercooler, and really to support that kind of power from 6.6L, you need an aftercooler. I ran mine pretty much on short test runs until the intercooler became heat soaked...

It would be great to be able to get a 400 hp diesel that would fit roughly in BBC dimensions, and not be excessively heavy. A 440 hp Yanmar weighs in at nearly 1200 lb, without transmission or fluids. CAT 3126B comes in at near 1800 lb. Then, you have to consider that if you want to use a stern drive, a Speedmaster is pretty much it for being able to get the right gear ratios, and handle the torque. Diesel+Bravo=Blown Bravo...

The long and the short of it is, unless you go for some exotic Seatek motors, your twin engined speedboat is going to gain at least 1000 lb in the repower. To keep the CG where it needs to be, you will have to add more weight to the nose. If you want a diesel-powered speedboat, you need to design yourself one from the outset, or better yet, call a Naval Architect like me, and I'll design you one... If you want my honest opinion, if you want to burn diesel, get a surplus turbine from MTT or elsewhere, get thee to a milling machine, and make it work... There are some nice little 600 hp units that you can practically carry down the dock by yourself.

Did no one look at this site??
They marinized the hummer engine.

the 6.2/6.5 gm diesel is a pos. wait for someone to marinize a 5.9 cummins to replace bbc, then you wont have a big weight gain and you can make big torque with it

Has anyone looked into these? They look interesting. Don't know the price though.

http://www.perfprotech.com/home/marine-diesel.htm