We have worked on a few conversions in bigger boats 40+FT. One customer has been VERY happy and is getting almost triple the fuel economy of his gasser engines he replaced. As a matter of fact when a bunch of dealers/manufactures went to FL (for a cruise) in the beginnner of this year they got to go for a ride on this boat and raved about how well it ran.
Duramax in powerboat
- Thread starter Jorekore
- Start date
Have you had any problems with the allison in boats or the dmax? Did you still use the allison trans in those bigger boats? No need to lower the compression ratio because it is a commonrail and has already got lower compression ratio right?
I'm only looking to get 450hp out of them to get a good Cruise boat, with twin 425hp cat 3208ta and surface drives the topspeed is near 50knots and that is way more heavy engines than the dmax. With triple 420 mercs and trs drives the boat weight almost 15000lb and with twin cat i think 16500lb.
I can't see any reasons why this engine would not be the best diesel for boats, a company in Sweden sell marine dmax with up to 500hp and theyre working on a twin lysholm supercharger engine that should make 600hp but still theyre are to expensive for me to buy and not as fun as building them my self.
I believe there twin supercharged engine is the 500HP version, there 450HP is the top of the line using the stock VGT turbo. Also look at there duty ratings on them at that HP. The 450HP version does not have a very high duty cycle from them, whereas the 350HP I believe is teh biggest they offer with a commercial type rating on it. The lower weight is not a huge issue when your dealing with that much weight. Personally I would just go with a straight marine treans and not loose the extra HP with the ALLISON trans. And lowering teh compression is even better for a marine application where you run at full load all the time. For one to live at 450HP, you had better consider doing a mild build on the engines with some delipped LB& pistons or steel ones like mcrat talked about. Use at least an LBZ rod, and a balanced rotating assembly. There is a HUGE difference when you go from a 3,000 pound boat up to a 15,000 pound boat. And it will punish the engines. The DURAMAX should do the job, but I would keep the HP down to say 350-375 HP myself for longevity.
I'm in the process of researching the d max in a skiff. Mine will be a bit of a different application it will have a straight inboard. It's only a 25ft boat not very heavy. But their is very little about this setup. Don't want to hijack your thread but I'm in the same boat. For lack of a better term.
The only good thing about the 3208 cat is you can run them at wide open and don't have to worry about them coming apart. But as you said the are very heavy and bulky.
The only good thing about the 3208 cat is you can run them at wide open and don't have to worry about them coming apart. But as you said the are very heavy and bulky.
Let me rephase that, older Vac-controlled trannys don't work in boats. Of course the turbo 400s were in a 12,000 lbs Welcraft. Like I said I have no doubt the guys on here can make a Dmax work in anything and maybe 40hp is to little for a 21 but I do have a 17 whaler with a 50hp outboard fully of fishing gear. By gear I mean lobster traps and hauler (yes I need a bigger boat). I never said it would push it fast. Anyway Yamaha is pushing the same size and bigger boat with two waverunner motors. What make and model was this 40+ size boat in FL? I would like to see a video of that. I am just saying I would like to see this setup on a 28-32 footer on the open ocean in rough weather running all day. I didnt mean to offend anyone and I am not being a ball buster I really would love to see one in a boat with some weigh.
I think a velvet drive should work fine. I was going to put a b series cummins in ole girl. But a Duramax would be way cooler just need to figure out the logistics. How is gonna hold up? What will the manifolds and fresh water pumps cost?
Ok guys I got in touch with one of them, I invited him to join and post his thoughts about this conversion.
This is some quick info I got from him 33ft fishing boat, 16,500.00 lbs. Old engine setup .6 MPG (yes .6) 24-26 cruise speed and 36 peak speed (good day). Duramax conversion 2.0 MPG (yes 2.0) 32-34 cruise speed and about 45 MPH Peak speed, He said NO smoke and very quite.
He also said he would have made a few changes in the trans gears but I will let him post that up when he signs up.
This is some quick info I got from him 33ft fishing boat, 16,500.00 lbs. Old engine setup .6 MPG (yes .6) 24-26 cruise speed and 36 peak speed (good day). Duramax conversion 2.0 MPG (yes 2.0) 32-34 cruise speed and about 45 MPH Peak speed, He said NO smoke and very quite.
He also said he would have made a few changes in the trans gears but I will let him post that up when he signs up.
Dan have you guys ever done a straight drive?? Do you still need an Allison in this application.
Marine diesel Sweden do make a vgt500 and theyre building a twin supercharger engine, their engines are used by many people in bigger boats, even the military is using them in some boats.
About manifolds.. I've read somewere that Ford windsor marine manifolds should fit the dmax, i know i have the link somewere but can't find it now.
I also think that a velvet drive should work fine but it would be easier if the allison worked.
Good Dan.
Should'nt there be 6 mpg with dmax and 2mpg with original power?
What was done to those engines, original hp?
About manifolds.. I've read somewere that Ford windsor marine manifolds should fit the dmax, i know i have the link somewere but can't find it now.
I also think that a velvet drive should work fine but it would be easier if the allison worked.
Good Dan.
Should'nt there be 6 mpg with dmax and 2mpg with original power?
What was done to those engines, original hp?
If you keep the rpm lower for extended cruise periods-below 2200 rpm as a ball park and as Pat said derate the power, there is NO reason that a Dmax can't last in a boat. It's all about tuning, gearing and proper cooling. Controlling egt's and oil temp is key to getting it to live longer!
Also in a displacement hull boat, it is going to be like towing a big load up a hill all the time, but in a boat with a hull design that lets it get get up on top of the water, once it's on step the load will be less. Just think, how many times with a ski boat or pleasure boat have you pinned it out to get up on step and then throttled back to cruise? Almost always unless there are a ton of people and booze in the boat!
Or if it is under-powered! Just sayin' I wouldn't be scared to do a Dmax in a boat-just do your research first!
Also in a displacement hull boat, it is going to be like towing a big load up a hill all the time, but in a boat with a hull design that lets it get get up on top of the water, once it's on step the load will be less. Just think, how many times with a ski boat or pleasure boat have you pinned it out to get up on step and then throttled back to cruise? Almost always unless there are a ton of people and booze in the boat!
Or if it is under-powered! Just sayin' I wouldn't be scared to do a Dmax in a boat-just do your research first!
Why will the Allison be a better option? And where can I find more literature on this. I will be doing some trawling mostly running back and forth to the hunting camp. I think a d max would be perfect for what I need. But I don't want a 30000 engine in a 10000 dollar skiff if you know what I mean.
Is that fishing boat a conventional drive or inboard/outboard? Is the allison used? Cant wait to see it!
Now it's either to go with dmax or Iveco 8,1L diesels, i do want the dmax but i want to hear something from the guy with the 33ft who runs them, i have found a pair of arneson asd8 in Florida for 10k$ and that is a drive that can handle more than enough torque from a dmax, i ran them before in a chris cat 30' with 2x815hp engines and they will last for more than 1200hp.
Joakim
Joakim
Couple of things, outdrives.... The merc stuff that lasts is crazy expensive 100k +. Second the tailshaft should have no thrust load on it, the drives should take 100% of the thrust. Third, call CMI and get some turbo headers made up. Fourth, boat size isn't what determines load on the engine, prop diameter and pitch do. You could have a 40,000 lb boat, running the same engine load as a 2000lb skiff, obviously the props would be way different.
Which goes back to me saying that you could push a 21 footer with a 40 hp outboard, you just wont go anywhere fast. Also, On outdrives you better be close with the prop the lower legs and not that strong that I have seen. Maybe thats why the big boys are so much $$$
Drives like anything else should be rated for torque. HP is just a number.
As i said Arneson asd8 can handle much more torque than what a duramax delivers.