Marine Re-power with a Dmax
- Thread starter LBZ
- Start date
BBC weight depends allot on what material the heads,intake,exhaust,risers,water pump, if it even has one, are made of. Cast iron, aluminum, stainless,etc. Anyway can't wait to see some dmax's marinized. Good luck and post some pics.
The marinized DURAMAX from MARINE POWER DOES weigh less than a fully dressed BBC by about 80 pounds. It may be worth looking into there manifold and up pipe set-up for your marinazation as it appears the only thing special about there marinazation is the manifolds and up pipes. They simply put a water cooled stainless heat deflector over the turbo, run a MAF-less air induction with a K&N air filter on it, cast-iron manifolds and up pipes that are raw water cooled, and a BBC heat exchanger to cool just the engine. It doesn't look like a great marinazation to me for true saltwater useage, but would work great for a ski boat which is probably why they rate them so high. it appears most of there engines go into military watercraft for south AFRICA from what I can find on there company. Also keep in mind that CUMMINS turns out a 480HP version of the 5.9L and 6.7L for pleasure boat use, so a 450HP DURAMAX isn't that far out of the realm of believeability.
I would think a DURAMAX with delipped pistons, LBZ rods, lowered compression, and a decent turbo with sufficient cooling would last a decent life at 450HP even in a heavy boat. The outdrive is going to be your limiting factor though. the biggest engine CUMMINS will sell the BRAVO X diesel series drives for useage behind is a 230HP SEVERELY derated 5.9L jackshaft set-up, and this package is known to have a SHORT service life due to the torque tearing up the drive. With the kind of torque the DMAX will be putting out, you will WANT to go with either the IMCO set-up, or a KONRAD drive with a BAM modified trans. MARINE power sells a outdrive set-up as one of there packages. It uses the 350HP DURAMAX engine, a KONRAD 660 outdrive, and a BAM 900 modified BORG WARNER trans, but I have no idea how much the KONRAD and trans cost. But I don't think ANY BRAVO drive will hold up at all behind a DURAMAX, nor do I think the new YANMAR 370 stands a chance, and doubtful about even one of the VOLVO's holding up either. MERCURY does sell the NXT drive set-up with the 480HP CUMMINS set-up, but it is a surface drive type arrangement.
Im just trying to save you money. 10000 pounds + Diesel torque (even with no tune)+ finding the right Prop = Outdrive goes boom. Even if you get all that worked out, My LBZ working hard sucks down the diesel which in my area is more then gas by about 40 cents. This thread was started looking for less gph, how much are you going to spend to save? Not to mention resale of the boat and parts to fix. At my marina, a guy about 8 years ago spent $8000 to but a new diesel in a sailboat. Right now that diesel has about 25 hours on it and he cant get $2000 for the boat. He ended up giving the boat to us as no one was interested. I like how everyone on here is wicked (Boston) talented and hey I hope it works out for you. Keep us posted. :shots:
I'll have to agree with the people who are all concerned about your outdrive. I am just finishing repowering my boat, and I had my 496 HOs (425 hp) rebuilt to 525s with about 575 hp and probably around 600 lb. ft. of torque. I am sticking with Bravo 3 XR drives, but I am having them rebuilt by All American Drive Service out of Michigan. They take all the Bravo 3 XR parts, treat them cryogenically, and put them back together better than stock (for close to the same price as a new XR drive), and he guarantees them to handle at least 650 hp. Pluse they have a 2 year warranty. I will still have to be nice to these drives (by easying the power on slowly) or they could have a short life. I will let you know how they work this summer if you are interested, but it is sooo easy to get 600+ lb. ft. out of a duramax, and it comes at such low rpm, that it is difficult to see a bravo drive living through it for long.
And with a diesel it's not just the drive you have to worry about. Don't forget about the differrent gimble housings that go into these as well. That low RPM torque is the reason MERCRUSIER came out with the DIESEL X series gimbles with beefier pieces in it. The low RPM torque is the killer. As for fuel consumption, a diesel will use less than a gas engine will, plain and simple. There are more BTU's in a gallon of diesel than a gallon of gas. The question is though, will he EVER save enough to justify the upgrade cost? Or are you doing it for the added range?
Never said a Gas would do better GPH. I said gas itself is cheaper and will the a diesel run that much better GPH wise to gain back the difference. More maint. on the diesel. What does a "Diesel X" drive run? The power the motor makes is not the only reason why the drive will come apart. He said they are fishing and trolling. Do they intend to not use the troller thinking the diesel will save money? The in and out of gear will destory the case as well. The prop will need alot of bite as the diesel tachs out earlier but has the power to spin a bigger pitch prop. In turn it may push the boat faster then they want at idle. We have a guy at our dock running a 454 drive in front of a stock 350 as a small pot hauler. Even with the HD drive the 350 beats it up with the in and out of gear. The drive is rebuilt ever 3-4 months. Of all the boat setup the fact remains that inboard-outboard are the weakest. Outboards are better but a regular inboard set up is the strongest. 
What type of boat did you just repower? Also, please educate me on the Bravo 3 XR drive versus the Bravo 1 XR drive? Which one is beefier?
BRAVO 1 is a single prop up to about a 15 1/2" diamter, BRAVO 2 is up to a 20" diameter single prop, and BRAVO 3 is a duo prop up to about a 15.5" diameter. As far as strength goes, there all about the same. The problem is though that even the BRAVO X drives with hardened gears will not live behind a V-6 diesel of 4.2L and 300HP(around 450 foot pounds of torque), so how do you expect it to live behind even a detuned DMAX at say 250HP and 500 foot pounds of torque down lower in the RPM band? Theres a reason that YANMAR came out with there own outdrives for anything bigger than a 4 cylinder diesel. And unless he plans on running it say 2,000 hours a year, he will never recover the cost of the conversion, let alone higher maintence costs. If it was mine I would be looking at a MARINE POWER 6.0L conversion for it. Lighter weight, more HP, only a slight loss in torque, will allow the current outdrive to live a long life, and reduced fuel consumption with it's closed loop ECM set-up.
I have a 37 foot formula 370 ss. The weighs about 16,000 pounds. I'm hoping for 60-65 MPH.
:he XR dives are the strongest bravos. The bravo 1s are stronger than the bravo 3, but not as good pushing aheavy boat. Bravo 2s are generally for big slow boats.
Well it all doesn't matter now.
He bought a 2006 Aluminum Hull 28' Boat in Ontario that has never seen salt water.
So he's selling the Bayliner and the engine that he just had built.
I have an ad up for the engine here:
http://www.duramaxdiesels.com/forum/showthread.php?p=791742#post791742
FWIW all you nay sayers about the drive not holding up, it's already been done and holding up. A guy in Vancouver who my buddy has been working with on the re-power replaced a 12V in a 32' Chris Craft using older but the same model of drive parts we were planning to use. He bought a Marine Power Dmax. Swap cost the guy a pile but 5 years later and 500hrs on it he has had little to no issues. 250-275hp, 650ftlbs torque, saw a 25% savings in fuel consumption after the offset of the fuel cost difference.
The total cost of this swap was going to cost the same as rebuilding the BBC with all aluminum engine components to lighten it up. Right now, it's all heavy cast.
He bought a 2006 Aluminum Hull 28' Boat in Ontario that has never seen salt water.
So he's selling the Bayliner and the engine that he just had built.
I have an ad up for the engine here:
http://www.duramaxdiesels.com/forum/showthread.php?p=791742#post791742
FWIW all you nay sayers about the drive not holding up, it's already been done and holding up. A guy in Vancouver who my buddy has been working with on the re-power replaced a 12V in a 32' Chris Craft using older but the same model of drive parts we were planning to use. He bought a Marine Power Dmax. Swap cost the guy a pile but 5 years later and 500hrs on it he has had little to no issues. 250-275hp, 650ftlbs torque, saw a 25% savings in fuel consumption after the offset of the fuel cost difference.
The total cost of this swap was going to cost the same as rebuilding the BBC with all aluminum engine components to lighten it up. Right now, it's all heavy cast.