DIY - Duramax Marinisation
 

Being between personal builds, I've been helping out on a couple new 6.6L Duramax marinisation projects over the winter. Since I've logged the most hours on the water and under the hatch with this platform, figured some of you might be interested in seeing what's actually involved these swaps.

The first build is a 33' Sonic [deep V cruiser] with a single700hp twin turbo Duramax, mated to 6spd Allison trans, an a ASD #8 drive. https://youtu.be/eGwc9gZMmx0
That one is a true DIY boaters build whose previous works include a T56 turbine powered cat. Which turns out had an easier learning curve than this diesel build. After a small catastrophic engine failure, the lessons learned here will ultimately make this a "how to" example for anyone looking to do a similar swap in the future.

The second boat is a larger center console fishing boat with two mildly modified [stock bottom end] 2014 LML's connected to Merc #6 drives. This one is more of a classic BBC to Duramax diesel engine swap. It includes a more "plug N play" approach with a custom engine harness and drive by wire helm. The way I'd like to assemble a simple swap kit to make this a couple weekend project, rather than a full on re-rigging job.

Campaigning my own one-off marinisation for several years, the question ask the most was; How much does it cost to convert a Duramax to marine use. Truth of that, to date, far more than buying a brand new 6.6L Duramax from the GM factory... Hence the main reason you don't see many of them out there. Less than 10 [non-military] builds that I know of. And yes today you can buy a fully marinised 500hp Duramax for a little over 30k, and drop another 30+ into a matching outdrive to handle it. But for that same money you can build a healthy BBC and buy a lot of fuel to feed it...

So I started this thread to explain how these swaps can be done right, and on a budget. Hopefully simplifying this reliable diesel platform that out performs the larger cubes BBC in all areas, for less than that new crate motor. To do this we'll take to look at each part of the marinisation process required to keep this swap clean, reliable, and affordable.

http://altfuelsgroup.org/pictures/al...Boat-Eng-1.jpg

good stuff,thanks for posting.how about posting more pictures.

Ok lets start with the easy parts for a BBC swap. Things you won't need to buy..

Luckily the typical light duty 2500-3500 series Duramax equipped trucks and a BBC share bell a housing bolt patterns. So your std Bravo rear mount and HP dampener will bolt right up.

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For those looking to run a larger marine trans like ZF, the Duramax uses a adapter plate between the block and transmission. This means you can switch from GM to SAE bolt pattern bell housings by boneyard or eBay shopping. These SAE 30 adapters were used in medium duty 4500 series and and up.

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Flywheel options, are just that. All the builds I been involved with so far have used a custom $1200 billet flywheel drilled to match the Merc rubber dampener or velvet drive dampener. I do know of a boat running a factory flex plate without issue. But because of the engine torque and spinning inertia, I would likely stick with something heavier. But in the $600 range.. More on this one later.

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That pretty much covers the rear of the engine. Now onto the front of our engines.

Once again, no big purchases required. Only a custom Merc seawater pump bracket and new serpentine belt is required.

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The factory alternator and power steering pump will work just fine. Because it's diesel, no special marine starter or alternator is required to be USCG leagal for these swaps. But there is an actual part number for a marine starter I found...

You can also leave or remove the AC compressor without issue. In my first post, see pic of my engine, notice the ECM is mounted where the AC pump would typically be found. However if I was converting a boat with a cabin, I'd keep one AC compressor connected and put that puppy to good use. Factory water pump on the Duramax is gear driven off the crank, so belt routing options are wide open. There is several idler positions that will let you delete everything keeping just alternator and seawater pump if no PS pump is required. Typical seawater pump location is shown in pic the below.

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More to come.

Good stuff man, keep it coming

Couple other pieces that can be used off the gas engine depends on your current rigging setup. The front motor mounts on my setup were factory Merc BBC mounts. Two of the block bolt holes lined up perfectly, while a third was re-drilled. My stringer width required a piece of angle on each side to center up the engine. Believe that was same as the factory though.

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PPE sells a Duramx set with adjustable stringer mounts included But access to some basic machining tools can save ya $500.

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My buddy Dave designed his own mounts to match his stringers [below]. While the twin engine setup is going with an offshore style mounting which I'll try to get a pic of when they get dropped in. The Duramax block has a couple different mounting patterns on each side, so it's really up to what fits your engine bay.

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very cool info !!!

Received these custom DIY motor mount pics to share.

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As you can see, getting the Duramax bolted up in a boat is probably the easiest part of this swap. There is two factory oil pan options, regular 10qrt and medium duty 12qrt designs. The 10qrt setup ends up holding about 12 with remote filter and cooler. And for those needing a lower CG, or looking to do serous off shore running, a dry sump pan is also available from multiple suppliers.

Ken here's a template for bolting a two or three stage BBC pump to the front of the block. When you get time to talk about the control and tuning please explain why it's important to start with the right series engines.
I started with LML's not knowing their ECM's are too complicated for a stand alone harness unlike the earlier series Duramax's. The fix was to swap out the fuel system for LBZ

Killer!

Thanks for the taking the time to share your expertise.

Love the marinised diesels.

GREAT POST !!! What are your thoughts on using a crank mounted Sea Water pump as Volvo uses on their conversions as opposed to a belt driven pump ? Just curious..

I don't see why it couldn't work if your running an aftermarket dampener. But the OEM unit doesn't have a flat mounting surface, or any bolt holes to connect the pump. Since the belt track is built into the dampener ring, GM never expected extra pulley's or hardware.

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I've found no major disadvantage to the belt driven pumps on this platform. Mine has logged 300+ hours on the same belt, and about 4 impellers. However changing those impellers was always a pain in the ....

Hoodoo is using a nice multi-stage setup on his build. Dave uses a double in/out design on his Sonic. So it's really up to your rigging requirements. Just remember, as I'll get into later, these engine do require substantial water volume..

The OEM pump is gear driven, but not positive displacement. So it's good enough for a closed loop system, or as secondary in raw water cooling setups.

http://econtent.autozone.com:24991/z...52801cac68.gif

Pretty reliable pump, and that's good. Cause changing that pump requires removing the dampener with 270ftlb of torque on the bolt, plus a special puller and new front seal. Not something your gonna enjoy doing in the boat. So I'd suggest changing it during your marinisation process. You can also easily delete and block it off if your cooling setup is fully belt driven.

Thanks...understood. I think the volume would be satisfactory but the mounting logistics might make it more trouble than it's worth. The crank driven pumps do work well...I used them on my twin SBC Vortec/Bravo I conversion from Pre Vortec/Pre Alpha. When I'm running on the hose thru the drive the suction will implode/collapse most garden hoses. I started with 140* thermostats and ended up with 160*s because even in 85* water the engines ran too cool !!

I had a Sea Ray 39EC a few years ago with twin 502 gas motors and often thought about dropping a pair of Dura Max Diesels in it. Those boats as well as 34EC's are plentiful and cheap and would make great boats for this conversion...it's really got me thinking...running thru a pair of ZF Transmissions would be sweet.

What's a fair average price I could expect to pay for a decent conversion candidate Dura Max in a salvage yard?

Thanks again for the thread.

Great question !! Depends on year, mileage, and how much you expect to invest after the purchase...

Since all model years share the same same basic block, head, and turbo configuration, it comes down to picking the best internals, fuel system, and electronics for marinisation. This is where it gets a little tricky, as hoodoo can attest.

Newer is not always better when it comes to Duramax engine swap models. The internals keep getting better, while the rest keeps getting more complicated. They all weigh in at about 850lbs, but some years are definitely better than others for several reasons.

So hear is a specs breakdown I borrowed from:
http://www.duramaxhub.com/duramax-timeline.html

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The early years like [LB7] are most abundant, but the fuel system had some serious issues. Injectors are mounted under the valve covers and prone to leaking fuel into the oil system. It also used a wastegated turbo rather than the VNT model introduced in mid 2004. On a good note, it didn't have an EGR cooler.. I'd personally avoid them for marine swaps.

2004.5-2006 LLY, this is what I owned, and the first Duramax on record to be marinized. That said, I'd skip it too. LOL... Seriously it's a great engine platform if you dump a little cash in them. Better fueling than the LB7, but still shared pistons, rods, and a 17.5CR. Which produced some bent rods and crack pistons. The LLY also used an ECM / FICM combo like the LB7. More electronics to fail.

Next you have the LBZ in 2006-2007.5. Isuzu/GM made some great internal and external improvements on this model. Better rods, pistons, and lowered the CR to 16.8. New stand alone ECM and improved injectors also. This is the year most Duramax swap projects start looking for. There was no DPF systems yet, so nothing to delete that requires special ECM tuning.. On this year, just add some head studs and run that thing at 500hp all day long..

The LMM came along in 2007.5 and ran thru 2010. This is my favorite model year, because it's abundant and basically identical to the LBZ inside. ECM operating system was changed and the exhaust DPF crap was added. But if your dropping one into a boat, it's gonna be running custom ECM tuning anyways. From 2007 to present all models share a common HS GMLAN CANbus network that allows simple translation to your modern gauges or chart plotters.. More on this later too.

Last is the 2011 and newer LML models. The most powerful 6.6l model to date includes improvements to the block, rods, oiling, turbo, fueling [debatable], along with GM's feeble attempt to lock the ECM down so no one can peal off the exhaust and crank em up to 800hp like previous models. This is where things can get expensive.
Yes it's a great bottom end, but a bit tricky to yank out of a truck and drop in a boat without a few techie buddies... Plus while not heavily advertised, the newly upgraded CP4 fuel pumps have been known to randomly grenade and gut the whole fuel system.. But they can be still marinized.

Hoodoo has 2 "beautiful" LML/LBZ/LMM models setting on stands just waiting to hit the water. Maybe he will share some more pictures.:whistle:

So the short answer for sprink58, $5,000...

A completely non-bias model year comparison is available at: http://www.trucktrend.com/cool-truck...diesel-engine/

Ok let say you've found a good deal on a average mileage Duramax donor. What should you keep off the truck? Or if you purchase an engine only, what will you get?

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Here is an average engine as removed from the truck. The engine harness disconnects with 2 large weather tight plugs, and one master 12v power breaker lug. The majority of our required sensors is on this harness. However the ECM and accelerator pedal sensor are part of a second harness typically not included with an engine only.

The fuel system feed and return line are quick disconnects, and belt accessories and starter all remain intact. About everything required should be on there. Exhaust manifolds up pipes and turbo also typically come with a complete engine. While we might not use all of it, is good to have for reference.

Next is what to remove, and what to upgrade.

Keep it coming, this is great info, I am a duramax nut and have thought about doing this for several years knowing the type of power these motors are capable of. I'm glad you are sharing this info with all of us here. Hats off to you

Thanks much.

My first Duramax experience was the one in my boat...So I learned about this the hard way, breaking stuff then asking guys who drag race or truck pull them why it wouldn't hold up.. LOL.

It took a few attempts to get all the bugs worked out, but once I did, no more problems. And these things will run with a 800hp blown BBC till their tanks run dry. Then you can boat another day or two on your own..

Just asking out of curiosity, what kind of drive holds up to all that torque ?

Another great question. Which I plan to discuss in much more detail later.

For now let me say, smaller than than a ASD8, it's gonna require some upgrades. Gearing is a huge unresolved issue I feel needs addressed. And a big reason I wanted to share how to get most bang for the buck on initial rigging investment.

Below is the XR that came with my 21' Warlock, handling about 675hp / 1300ft lbs. Drive was installed new in 2006, upgraded by IMCO a month later, and currently around 350 [flat water] hours on it. I also know of a similar weight boat running a pretty much stock Bravo1 behind a 500hp Duramax.

One nice advantage to this platform, you can power slope or torque limit the RPM curves with a laptop. Along with option to add 5 switchable on the fly power levels. So you could setup a 400hp tune with 700ft lb torque limits above 2600rpm for offshore running, then flip a switch to a 600hp/1200ft lb tune that spins 4000R's on flat water.

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Cool

Ok so back to the Duramax disassembly process. But first, you should try to gain an overview on the engine internals, turbo and fuel system. Unless buying a new or reman crate motor, your gonna need to know what you have to start with.

50k miles on this engine is barley broken in. I know of a bone stock one that hit 900k without a valve cover removed.. So even a mid 100k mile Duramax could be a direct drop in that runs great for many years of boating. But it all depends on what your looking to do with it.

If possible you should check it running. First the normal stuff like excessive smoke [at idle], leaks or blow by. Also a good time to plug in a scan tool or OBD tool like Torque to check DTCs and perform a Balance Rate Test

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Balance rate measures how much fuel the ECM adds or subtracts from each cylinder to idle smoothly. While typically used to isolate bad injectors, it can also expose low compression. As does white smoke at idle.

The next check before striping anything off is to do a compression test. This can be done while in the truck, or just as easily setting on the ground. You can even use the $30 compression test kit from Harbor Freight that comes with the correct head fitting. Removing the glow plugs is pictured below.

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Now you know what ya have, power wash and stick it on an engine stand. Next we can start ripping parts off and getting to the fun stuff.

Don't know what this one ended up going for but around 6000$ is common for very low mileage

With the engine on a stand it's time to remove everything not going back into our boat. This includes the obvious parts like cooling fan and AC compressor, along with a majority of the factory air intake system, EGR valve and cooler. Will also be upgrading the factory oil cooler and filter housing in this process. The exhaust manifolds, up-pipes, and turbo can also be removed at this point. You should take some photo's and tag all the electrical connectors before removing the engine harness. It's best to leave the fuel system between the CP3 and injectors sealed up to avoid contamination until next stage in the process.

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Start by removing the wiring harness. The glow plug control module [rear drivers side in pic] can be set aside for now. Glow plugs are actually optional in our marinized Duramax.

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The EGR cooler is mounted up top, where passenger side up pipe splits off by the turbo in first picture above. The up pipes bolt to the turbo and manifolds with 3 12pt bolts per flange. Save those gaskets, we may use them again. In the second pic the cooler is the shiny looking cylinder beside the turbo. Several different designs have been used since 2004, all in the same location, and all going to the scrap pile..

Next pieces to come off will be the main intake with pre-heater, throttle valve, and EGR system.

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Again several different intake setups were used over the years. But for our marine build most of this is not going back on the engine. Do save the MAP sensor [top front in first pic] because that we will use again. Plan is to replace all this factory [mostly emissions related] stuff with a clean and simple Y-pipe that allows us to connect the charge cooler tube to our cylinder heads. Depending on final air charge cooler placement, you can purchase a off the shelf Y-pipe, or build your own from the parts we just removed.

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Great job! I'll be following.

Ok you should have 2 piles of parts by now, things your gonna use and the scarps. Before we pull the turbo off lets get more easy stuff out of the way.

On the passenger side you'll find the fuel filter assembly, remove the rubber lines and unbolt the two bolts facing the filter. Toss it in the keep pile, for now. From each valve cover you have a crank case vent tube tee's into the turbo inlet [second pic]. Remove that tube and toss in the scrap pile, it gets marinized also.

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Then moving to front of engine, if planning on removing the heads we may as well remove all the accessories, brackets, idlers and thermostat housing. Depending on year and model, the thermostat housing may have a removable [black steel] discharge tube that you want to keep. The Duramax uses two thermostats that open at different temperatures. You can change those based on an open or closed loop cooling application. The complete housing assembly cleanly bolts to the front of the heads with a small recirculation tube down to the water pump.

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Once all of that's out of the way, you can see the common rail high pressure CP3 fuel pump. Unless upgrading the pump or tearing it down further, just cap off the hose barbs that connect the fuel filter housing and fuel return line for now. As you can see they did a good job of hiding this sucker, luckily they seldom fail...

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That takes us down to the turbo and common rail fuel system left on top the engine. From here it gets easy..

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From a good "how to" write up on Duramax Forum that goes into the Turbo removal details. Its basically 3 bolts, 2 electrical plugs, 2 water cooling tubes, and oil pressure and return lines. The exhaust we took off earlier. We can set that puppy on the shelf, or send it out to be cleaned and inspected.

Next I want to move to the oil cooler and leave the fuel injectors alone. This is because unless your tearing the heads off, it's safer to leave the fuel system sealed up. Can't say the same for the OEM oil cooler setup, it's out of here. Not a terrible design, just to too small and a bad location for marine use.

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You may have noticed the cooler / filter combo is connected directly to our water pump up front. This is because the Duramax coolant flows from the front to the back of the engine before entering the block. So while we plan to upgrade our cooler and relocate the oil filter, we also need replace that coolant routing tube. There is several kits on the market to relocate the oil filter, but only a couple that fit our marine build and Duramax block.

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All the builds I've worked on to date shared this adapter from PPE. Their cooler delete kit consists of a CNC machined block adapter threaded for AN fittings. They also include an adapter plate to reconnect the coolant tube to rear adapter plate. This setup allows removing the filter/cooler assembly, but retains the oem tube from the water pump. It can be improved upon, but for now our primary goal is to get the oiling upgraded to marine standards.

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Internal Upgrades
 

If you've purchased a good clean low mileage 07 or newer engine and can live happily with around 500hp, then there is no need to dive any deeper into your engine. You can buy a fully marinized Duramax from MarineDiesel Sweden rated between 400-500hp, rest assured it came straight off the same production line in Dayton OH too.
:flag:

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So if that's good enough power, bank $10k, and skip this section. You can go to the next page when I pick back up at fuel system upgrades. Here is a list we are going to address along the way.

• Internal Upgrades
• Oiling System
• Fuel System
• Turbo Options
• Exhaust
• Cooling System
• Intake / Charge Cooling
• Electronics
• Transmission & Drives

For everyone else, lets rip the heads off and take a look at a stock Duramax internals.

You can now remove the hard steel fuel lines from the CP3 pump to the injectors and stick them in a large ziplock. The smaller black lines are fuel return, push in on the locking rings and they release from the injector top. The fuel rails unbolt from the primary intakes with two bolts, cap them off and store in a ziplock too. Just be sure to cap off all the fuel fittings so not to get any dirt in anything. Don't worry if you do, Inectors are only $300ea now...

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Once all the fuel lines are off you can unbolt the injector hold downs from the head. A 12mm socket if I recall, and the injector should slide up and out of the head with a little persuasion. This all depends on how much carbon is built up on the tip.. LABEL THEM by cylinder #, wrap in bubble wrap and store in a safe place.

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Next we can pull the 2-piece valve covers and unbolt the valvetrain. The Duramax uses a single solid roller lifter camshaft, connected to a rail type rocker arm setup, that operates 4 valves per cylinder. These OEM pieces will easily handle well into the 700-900hp range with a couple easy mods. Not bad for Isuzu...

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Interesting story on the Duramax joint venture https://history.gmheritagecenter.com...sel_6600_Story

Once you pull the heads we find the #1 point of failure in these engines turned up, the pistons. The first pic below is from my LLY engine when it still had stock pistons. The head studs are not factory. While the Duramax does employ a 6 bolt per cylinder clamping pattern, they also used torque- to-yield head bolts from factory. In fact 90% of the bolts on this engine are "single use" torque- to-yield.. So keep that in mind. Switching to good head studs will pretty much guarantee you'll never blow a gasket in the future.

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Next lets examine examples of piston failures. Couple from my own LLY, and one from Dave's marinized [stock bottom end] LMM. This is where industrial or marine standards part ways from light duty trucks. The OEM pistons used after 2006 in the LBZ/LMM were improved upon with a different bowl design and lower CR making them less prone to failure than LB7/LLY's. However they are all cast aluminum and won't handle prolonged abuse either. Abuse being high EGT's or long injector pulse width and a bunch of timing advance.

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Many drag racers and truck pullers have successfully pushed the OEM LBZ/LMM pistons well into 600-900hp range without failure. For 10-15 seconds at a time... They don't care much for 10-20 minutes of high RPM blasting that would be typical in a cranked up diesel boat. Even GM caught on to the cause and released a tech bulletin to alert dealers how to identify if someone was running a modified tune while under warranty.

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Not that long ago a 6.6l Duramax piston upgrade involved taking stock pistons and cutting the bowl lip back to reduce the chance of cracking. Right after my second piston failure I lucked out and scored the first set of Mahle improved castings for testing. This new piston design included a reshaped bowl, better oil cooling passage, lower 16.5CR, valve reliefs and graphite coated skirts.

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These held up well for me, and are still in the boat today with around 350hrs at just over 650hp. Many of those hours at high RPM's for extended runs. While some racers have cracked them, they are actually rated to around 950hp. So we used this piston with a 16.0CR in Dave's new 700hp build. One of the original Duramax gurus has expanded on the design by taken this same piston and machined the bowl into an oval. This change along with ceramic coating the top has provided a piston that's so far been unbreakable. More on this Fingers Oval Bowl Duramax Performance Piston

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Many people ask "why not just run a forged piston?" It's actually not cost related, it's a longevity thing. Custom forged piston are now available and proven in 2000hp Duramax race engines. However the forge and machining process doesn't allow for using a hardened upper ringland like factory cast pistons. In the pic below you can see the "cheetah pattern" in the top of the cylinder wall. The upper portion of the linerless cylinder bore is induction hardened to reduce wear. Due to the very high heat and cylinder pressures, the forged aluminum piston ringland will actually wear out long before the rings.

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What we don't see yet for the Duramax is a "steel" Monotherm piston as use by Cummins and other industrial level manufactures in marine engines. I have a feeling a couple sets may be out there in engines for testing by another OSO member... But nothing officially has been released by Mahle to date.

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More about these Dmax piston designs at:

http://www.dieselarmy.com/engine-tec...otherm-piston/

http://www.duramaxforum.com/forum/af...pistons-2.html

Had to finish up a couple projects last week, so will try to catch up where I left off.

Next internal part we need to address is the connecting rods. Once again the choices depend a lot on the power level your looking to run, and engine model your starting with. HP / Torque limit on stock first generation LB7 LLY rods was considered to be about 600/1200 at the crankshaft. If you think about it, that's not bad for a 2001 OEM 403ci bottom end. And when they do fail, they usually just bend rather than break. The factory LBZ/LMM and LML rods were upgraded, and those have been pushed up to 800-900hp in trucks without failure.

For typical marine use I don't feel bending the stock rods are a huge concern, and here is why. I pushed factory LLY rods to almost 700hp in my boat without failure. In the chart below we can see the torque vs HP curve on a newer 2011+ LML engine. Look at the peak toque RPM, it's at 1600R's then falls off a good bit. My experience was a 4 blade 32P Bravo prop couldn't begin to hold that power and would blow out with full down trim. I switched to a 5x37 and even that would start to cavitate if you stabbed it. So my theory is, these rods typically fail at peak torque RPM, and if you can't hook up that torque in a boat, then you can't bend them...

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While bending stock rods at double factory rated power isn't a big concern, there is still a slight problem with them. And this one you won't find much about on the Dmax forums either, cause it typically only occurs in boats.. Wrist pin bushing wear... I was made aware of this by a very well known engine builder who is likely the first guy to ever marinize a Dmax. Curtis Halvorson at Extreme Engine Development in Calgary, Alberta, Canada. When I was ready to give up on the Duramax boat, this guy reeled in my expectations and pointed me in the right direction. I followed his advice and try to pass along everything he taught me.

Curtis tried spinning a pair of LB7 engines 5k all day in a race boat way back in like 2005. He told me he was only getting 100hrs on wrist pin bushings. So when I tore my engine down to upgrade pistons, we checked the pins and bushings closely. He was spot on, rod bushings were about shot with only 100hrs of high RPM boating on the stock bottom end. Curtis gave up on the whole marinisation idea BTW. Here is a video of his latest Dmax build though. https://youtu.be/0DRfjH-dVQI

What I took away from his advice was, 1) use a better bushing material, 2) increase the oiling to the pin, 3) stop trying to spin the engine 4000+ Rpm. You have to consider that in a truck this engine has a peak power range of 3000R, and red line of 3200R. While you can spin them 4k, it's not likely your gonna do that very long in a truck. Luckily the rod selection and options today are much better than my build date of 2010.

GM increased wrist pin dia on LBZ, and today the aftermarket rod selection is much better. You can now buy rods with pressurized piston pin oiling from at least two manufactures. Which I would certainly suggest for any build over 500hp. A good set of rods will run ya between $2400 - $4000. See the comparison picture below and see if you can spot the factory LB7/LLY rod. I will get into the "cheap fix" I used in the next post.


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Ok we have examined the two weakest internal parts, and here is the most important points I feel allows these engines to live or die in a marine environment. Oiling, Oiling, and Oiling...

A good read that explains this along with the different Dmax internal changes over the years can be found here.
http://www.sbintl.com/tech_library/a...max_diesel.pdf

In 2006 with the LBZ model release GM / Isuzu strengthened the connecting rod, along with increasing diameter of the piston pin, and adding bushings in the piston. Obviously they were aware of some weak points by examining common failures and felt the piston pin area needed to be addressed. I can't say for certain if these LBZ changes resolved the LB7/LLY pin bushing issue or not, because I've never tore one down that was used in a boat for any extended periods. However a simple mod I used on the LLY to increase piston cooling and pin oiling [which didn't cost me an extra dime] was to simply increase oil volume flowing into piston bowl cooling passage by some 30% or more.

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These cast pistons are oil cooled. While now becoming common in high performance gasoline marine engines, all modern diesel engines use oil squirters to remove the heat from the piston. In the first pic above, see the little copper tube pointing towards the piston. In the second photo it's labeled (A). This squirter takes oil from the main rail and sprays it directly into a hole under the piston [pic3] when it reaches bottom dead center. There is a cavity in the piston under the bowl that drains back onto the rod. In top of the rod, there is two holes that oil the pin bushing. See where this is going?

That little copper squirter tube is crimped down on the tip to reduce the oil flow, so to increase flow we drill it out. Some salt flats racers have even found that by adding a second squirter and modifying the piston to accept 2 of them has stopped most piston failures. In the base or bolt area of the squirter GM uses a small spring and ball to stop the flow of oil if rail pressure drops below 30psi. So at hot idle, they don't flow any oil into the piston cavity. I can't say for certain if that mattered, but both of my stock piston failures came right after a long idle period, within 10 seconds, soon as I jumped hard on the throttle. Like they heat soaked and couldn't cool quick enough when I put the fuel to it.

But if you remove that ball and spring, you'll need a better oil pump setup, or idle pressure will drop below a safe level. Eight of those little tubes move some oil volumes. So for my build we left the check balls in place and just drilled out the tips. It sure didn't hurt anything... This is another point that Curtis from my last post turned me onto. I recently had a long discussion about this mod with the company owner who originally maninized my boat while helping chose components for my friend Dave's new engine. These guys build a bunch of Dmax engines and had never modified those oil squirters before, and claimed we would have to switch to a dry sump oiling. To which I replied; "If you recall I fixed all your screw ups some five years ago, and my engine is still running strong at 350hrs. How many hours is on your boat engine again?" LOL.. He agreed to the modification with my specs and a stock oil pump.

I found this MaxTorque.com study on oil cooling and the Duramax from 2008 that explains these principles and shortcomings with the factory oil cooler setup. This graph below fits well, and shows why we need to change coolers and monitor oil temps our Dmax conversions.

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From the study. The most notable result from the 2001 SAE Study is the effect of RPM on oil temperatures. The effect of doubling RPM, with no additional workload, raises oil sump temperatures 54 degrees! This effect is explained with a couple of phenomena. There is more friction, obviously. But also, oil flow rate (and thus heat transfer) rises almost linearly with RPM.

Oil flow and sufficient oil cooling is the life blood of any marine diesel engine...

So far we have covered the major internal upgrades for those looking to exceed 500HP marinized. Along with the simple oil squirter mod I would do to any stock engine before dropping one in a boat. Only a couple last points to address on the internals, then we can button it up.

If you've decided to tear the engine down for anything above, you need to KEY THE CRANK & CAMSHAFT while in there. For unknown reasons GM / Isuzu thought it would be OK to use a small roll pins to align the crank and cam gears. The stock cam itself is cut from billet steel with a profile that's typically good for 800-1000+hp without question. There is aftermarket profiles to raise operating RPM range, along with an alternate firing order option that came about to address harmonics felt to be causing broken crankshafts. While it makes for good opinion based topics on the Dmax forums, I just can't see spending $1500 on a camshaft unless there is some major performance gains... One thing everyone can agree on is the factory pin setup should be address for any performance application.

Below is some pics of the stock cam vs a keyed cam. I did mine [last pic] on the first tear down using a 50yr old milling machine in a buddies garage. There is plenty of online shops that will do this mod on your cam or even offer cam exchanges for around $150. I would highly advise it just to be safe.

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While not as prone to failure, if you have the crank out you may as well key it also.

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The rest of the bottom end is pretty good to go from factory. The main caps are cross bolted into the block, so it's not likely they can walk. Just remember to replace those torque-to-yield bolts. If you want added insurance, SoCal Diesel makes this stud girdle setup.

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Last point is to use good aftermarket rod and main bearings. I used the H series bearings back in 2010, but there may be better materials out by now. Also check out the oil pick up tube, no upgrades needed there.

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OK...so now I'm neck deep in the theory and application. Understanding that marine application is a full time bearing and wrist pin load I see where those parts that are sufficient for an automotive application will fail prematurely in a marine environment. I suppose it comes down to inferior metallurgy yielding to improved superior metallurgy for the application.

What I'm trying to wrap my head around is why the 32" and stronger bite props are blowing out with these huge applications of TQ. Seems that the answer would be in a larger diameter prop if I understand hydro dynamics at all.

Thanks for all the information...great read !!

Yeah its all that low end torque when the turbo lights off at around 1500rpm if your on the throttle. Engine goes from 400ft lbs to 1200ft lbs in under couple seconds. Soon as that prop starts to boiling the edges, its done. Bravo1 drives being limited to just under 15.5" diameter props, and 36" pitch off the shelf options doesn't help. That 4 blade 32P at 15" dia I first ran was like a 13" radial on a drag car. You can drive on it, just don't jump on the throttle.

Once I changed to 15.5" with 5 blades and stepped up to 35 pitch it wouldn't blow out, but you could still feel it cavitate until you backed off the throttle for a second. I see this same thing happening on my friends boat with the 6spd Allison and ASD8 between shifts. He can log the output shaft speeds, and that surface piercing prop will jump like 600-700rpm when shifted from 4th to 5th [OD]. After 5 or 10 seconds you can see it slow back down and hook up again in the logs. It's a torque thing...

The easy fix, that also helps protect the Bravo drives is using the ECM's torque limit table to map power curve by RPM. Once I modified the torque table you could slam the throttle down from a dead stop and she would climb nice and mellow until up on plane. [See Pic Below] Above 2000 R's I left it maxed out and unrestricted. After breaking the shift lever bolt off inside the outdrive, I used that same table to limit idle torque to 50ft lbs. Nice feature you get with EFIlive...

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With the new internals installed there's not much left to do but button it up. Depending on cooling system plans, you may wish to switch to appropriate freeze plugs at this time. Stock cylinder heads are fine for most applications. At minimum they should be inspected, cleaned, and trued before reassembly. One safety upgrade might be switching to titanium keepers.

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Also now is a good time to paint the block and powder coat all the covers, intakes, and brackets if you want. Just be sure that who ever does the powder coating plugs all the bolt holes and masks off mating edges. I forgot to stress that, and it became an issue on assembly. Should also be noted that the oil pan, intakes, and front cover don't have gaskets. These parts use grey GM engine RTV sealant. Only the two piece valve covers actually have gaskets.

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Last two points worth covering are regarding the crank damper and factory fan mount / idler pulley. The factory crank pulley and damper assembly does ok in most lower HP applications. Since we have keyed the crank, spinning the ring is only possible issue. I paint marked my damper after assembly to catch any movement. If not keyed and the pin sheers, they will pick up a violent vibration. For any high power application the ATI super damper is a good upgrade choice.

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The center pulley in normal location of a water pump on gas engines is actually just a cooling fan drive. It has a 1.5" long threaded snout that the cooling fan mounts on. When I moved the charge cooler to front of the engine, I was 1/2" short on space. So I chalked the pulley up in a band saw and removed that snout. This mod makes for a cleaner looking setup on any marinisation project.

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That concludes our internal upgrades section.

Curtis had me drill out the piston oilers on mine way back when also. Great info with the how's and whys.

Most Factory Marine Diesel engines have after coolers on them. How are addressing that issue?

Chris

[ATTACH=CONFIG]553860[/ATTACH][ATTACH=CONFIG]553861[/ATTACH]In comparison to a Seatek that makes 700-1200hp the rods look small, Seateks are only 6 cylinder though.