lets talk putting a diesel in a go fast boat..

M

matt440rev

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Ok, so here's my deal, I'm buying a hull project, and instead of the typical blown big blocks, I wana do either a single or twin disesels. I'm thinking of starting off with a 30' single engine scarab style, but a tiwn might be an option.

So, here's lies my concern. I wanna be able to run 100mph, not have to worry about egt's, and be fuel efficient at cruise for poker runs. All on a budget. I'm a 12v guy, and if I were to attempt it, id like to go that route, but, the duramax really intrest me too being light, stand alone computer, and easily turn big rpm's.

So here's my question, if it were your project, what motor (s) would you use in a boat? I was thinking if its a single to use a cummins with trip turbos, or a pair of dmax's. I like the idea of a electronic tuned motor like a cr cummins or dmax with the quiet too.


Let's hear some ideas.
 
Assuming the cummins would fit in the engine compartment lengthwise I would opt for it. Mostly due to cheaper costs. Somebody posted a fuel consumption chart for a 370hp marine 12v, they are not lite eaters..
 
How much HP are we talking to push a boat of that size to 100mph?
 
nwpadmax said:
How much HP are we talking to push a boat of that size to 100mph?
Click to expand...

I'm by no means a boat expert, but id have to say a single engine isn't feasable to do 100, probably 900hp with a diesel and the added weight. If it were twins id say a solid 700hp ea would do the trick. Propping would be a big hurdle because they don't spin the 6k rpms. In all honesty a good running 85mph boat would be great, but 100 would be sweet! Id idealy like a 750-850hp motor that wouldn't have any egt issues for poker runs.


This is just a project I'm consdering taking on this winter, and to keep the first boat in reality check with pricing, ill probably steer towards a single engine 30ish ft hull. Eventually by retirement id like to have a twin engine poker runner.

I just went out on one yesterday that was a 410 skater with 3,500hp and 160mph was 3/4 throttle!!!
 
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not to derail your idea, but I think your going to have weight issues. I have often thought of doing the same thing with two three rotor Wankel's with a two to one reduction drive on the output shafts, this would give you about six hundred HP and about a 1000 ft lbs of output on each engine.

Your total power would be 1200 HP and 2000 ft lbs of torque. Now to find some out-drives that can handle that kind of power.

The best part of this is that your weight would be much lower then a big block.

If you wanted to get really creative, they make rotary diesels !

Here's a video of one.

[ame="http://www.youtube.com/watch?v=bpxK2ub-qCs"]http://www.youtube.com/watch?v=bpxK2ub-qCs[/ame]
 
To push a v-bottom 30' hull, your gonna need more than 1000hp and even then that small of a boat is gonna be tough to fit those motors in and the cooling system, transmissions and then not gonna handle rough water that well. A good boat to start with would probably be a 35ft or so Fountain with a step hull. My dad used to have a 28' Eliminator Daytona Cat with Twin Merc Racing 500 EFIs and it would run 94ish. Now he has stepped up to a 36 Ft Eliminator Daytona Cat with the same engines newly refreshed making 512hp at the crank. Bravo XZ Drives. It barely runs 100. The Cummins in a really long motor and heavy, compared to the Dmax or BBC that my dads Merc 500 EFI is based off of. You'd probably need a pair of built Dmaxs pushing at least 600-700hp, if not more to run that fast. Then you run into the problem of gearing. My dads boat turns 5700 rpms at 100ish. The gearing is out there, but not sure a Bravo XZ Drive will handle the torque. I know a Mercury #6 Drive will handle it no doubt, but i don't think you'd be willing to drop a minimum of 25,000$ on each drive. Plus the Dmaxs will need to be built to handle the high RPMs for extended periods. All I can say is good luck.
 
Just buy the insane marine duramax Banks builds, or two of them if you're feeling like really going fast.
 
twin dmax's would be the way to go if you can make it work!

good luck with your project
 
bwdt said:
not to derail your idea, but I think your going to have weight issues. I have often thought of doing the same thing with two three rotor Wankel's with a two to one reduction drive on the output shafts, this would give you about six hundred HP and about a 1000 ft lbs of output on each engine.

Your total power would be 1200 HP and 2000 ft lbs of torque. Now to find some out-drives that can handle that kind of power.

The best part of this is that your weight would be much lower then a big block.

If you wanted to get really creative, they make rotary diesels !

Here's a video of one.

http://www.youtube.com/watch?v=bpxK2ub-qCs
Click to expand...


That's awesomeness!
 
I think the others had great advice.

Weight and power will be a major issue with a Cummins. Twin or triple turbos on a boat with limited space could be an issue, and I think a Cummins block weighs around 900 lbs without any accessories. Start hanging turbos and piping, and weight will add up quick. Also, gearing (RPM vs. what drive you choose) and EGT's will be an issue, trying for ~1000 hp, wide open for an extended period of time. Might want to look at a serious water injection, too.

Have you decided on how many engines you are going to use?

Good luck to you sir, let us know what you find out.
 
Lightweight and Fairly Powerful and reliable.
http://www.ilmor.com/en/marine/performance/MV10-725.aspx
MV10-625.jpg
 
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Fab up a an OD unit and put it on the back of the engine, if you have the room and get you the RPM you need!
 
couple things to add, a tunnel boat would be best, you have unlimited cooling of intake, w/a intercoolers, etc. and you guys are forgetting they have overdrives now for big power.. i think( ive dreamed of this for years now) a 33 or bigger tunnel(eliminator or htm) and some deap pockets it would be easy to go well over 100..
 
If you really want it to burn diesel & be fast and lightweight........turbine!

1000k hp and high RPM is nothing. Probably not so good on fuel for crusing though.
 
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