92 series Detroit Diesels

Speaking of landing craft. I worked full time for an owner that had a LRC 72' with Natural 12-71's and the exhaust exited out the sides right by the tiny pilothouse and that thing was SOOOOO noisy when it was running. I refused to run it for the owner. I always wanted to run it once, but knew if I did then the owner would ask me again to run it when his other Captains were busy. It only did 7. something knots I think and his shortest run was 50 miles each way to one of his island resorts. I preferred to only run the Sportfish I was full time on that did 31 knots....hehehe

The landing craft is a LCM8 I ran one in Panama in the winter of 1970/71 hauling liquid asphalt from Cristobel to Bogas del toro to build a runway, it had two sets of twin Gray Marine 6-71s coupled to an allison gearbox it ran 10 knots with two thousand gal of liquid asphalt in tanks in the well deck it had water-cooled mufflers. Other than a learning curve to compensate for steering something with a flat bottom it wasn't a bad ride at all

This one was 72' U.S. Navy and had twin 12v71's Naturals. It only ran 8 knots (a touch less with current), perhaps that's the way the engines were governed or that's all it did at the rpm's they ran it at. The owner had an island on Glover's Reef and dive resort on Turneffe island in Belize and they used it to bring equipment and supplies out to the islands to build small houses and a runway on Turneffe. This one was louder than loud, and I knew if I said yes to running it to Turneffe when his one Captain quit, I'd get stuck running it again and again. I think I have a picture of it somewhere. You could fit probably 4 trucks inside of it, it had some compartments accessed from the cargo area to the hull sides with waterproof doors that you could sleep in and stuff (if you really wanted to rough it).

I was very happy as a full time Captain on a 45' Cabo express with a full time Mate (at the time 2005). hehehehe.... No need to screw up a good thing!

Please make some enquiries and let me know.

I'm 67 and have been running 671s since I was 13. Generator engines before that. I don't think there is a more reliable engine of that size. No injector pump, no circuit boards, no electronics to fail at sea.
As to the 92/71 comparison, most 671 built were naturals (non turbo). 92s appeared when people were looking for more power in a small package. Depending on the operator, turbos are engine killers. Their purpose is to put more hp in a small space. Turbos create excessive heat at high rpm/hp settings. A 671 natural will go 3-4 times longer between overhaul than the turbo versions. I've seen naturals go beyond 20,000 hours. Figure it out, natural about 200 hp, 671 turbo above 450hp. Same block, more heat. At overhaul you'll see heat damage on short life pistons, valves and sometimes sleeves.
Because 92s came about to meet higher hp needs, it's not a fair comparison. Keep the rpm/hp down on the turbo engines and you'll double the time between overhauls.

LEPKE- I don't think it's an unfair comparison, because if you're looking at a boat with 92's, the 92's only came with turbo's and either a lot of fuel and boost or an excessive amount of fuel and boost (JT's usually). A lot of yachts also came with the 71 TIs. I agree Naturals go 2-4x longer than turbo'd, but you're usually only going to see Naturals in slow moving yachts such as trawlers.

Also a water pump or generator connected to say a 6-71 is probably the best thing to attach to it for lifespan compared to being installed in a bus or boat. A generator or water pump runs at 1800 rpms (or wherever the governer is set at, but a constant speed) and the oil and water temps stay the same so you don't have metals expanding and contracting a lot.

That being said, if you compare a similar 71 TI to a 92 TI, the 71's will generally last twice as long at least.

The issue with the 92's is they were developed for the military to have the most HP in the smallest/lightest package at the time. The military didn't care about longevity as they had a slew of mechanics that rebuilt them every 1000 hours. They weren't designed to be in service 10, 20 years between overhauls. This being said, they were designed to be taken apart and put back together easily, thus the o-ringed heads. The o-ringed heads cause a lot of failures if the coolant isn't changed every 2 years. The heads crack easily if overheated due to the larger bore size. And, the injector size is so large they tend to wash the liners and dilute the oil with fuel if run at low loads/idle rpms for a long time.

I always hear these low hour TBO estimates for 92 series engines and then wonder how we got 3800 hours on a pair of J&T 6V-92TA's in a 38 Blackfin and 4400 hours on a pair of 8V92TA's in a 44 Pacifica before rebuilding them - these blanket statements of low TBO's in this post just don't match with reality (mine).

Also got 4500 hours on a pair of J&T 6-71 Naturals before rebuilding them in a 42 Uniflite. although loved they way they sounded when you fired them up. Still would light off on the first crank even when they were tired.

The 92's seem to do ok in boats where they cruise at 25 knots or higher. I managed a 1987 63' Ocean with 12v92's that went 6,000 hours before majors and it was over-propped and towed a 35' Marlago behind it half the time, but cruised 26 knots. But in slower,heavier boats, where in a sea the cruise speed changes a lot and changing load factors and high load factors at the lower rpm ranges seems to really shorten their life. Boats that get up on plane easy and cruise at 25+ knots, they seem to last ok.

I've managed A LOT of 92 boats over the years. A 1994 54' Hatteras SF with ddec 12v92's, had 2 sets of majors by 1960 hours. I currently manage a 59' Baia with 8v92's, boat is a 1997 and it's also had 2 sets of majors in 1600 total hours, but REALLY loads up the motors at hull speeds. I managed a 58' Striker 1991 and by 2004 it had 8 sets of majors. A buddies 41' viking with 8v92's went 1600 hours before major. And on and on. Another issue is that a lot of the 92 blocks were out of spec as well, egg shaped bores, crooked deck surfaces where the cylinder heads bolt on, etc. etc. I was told D.D. tools and dies were a little worn and not replaced often enough sometimes. Keep in mind a set of any other brand (covington, S+S, etc.) of 671 naturals see a lifespan of 10,000-20,000 hours.

I understand that, but all of these companies marinized the engines differently. All of them used different fuel injectors, turbo's and other various parts in the marinizing process, some even used goofy injector timing. J+T generally put the largest injectors and turbo's to try to eake out the most HP possibly out of an engine compared to the other marinizers and generally have the shortest life between majors compared to the others. D.D. ended up putting an end to the process of the dealers sizing/installing injectors and turbo's on the engines when they came out with the DDEC's around 1994 I think it was. Prior to that D.D. sold the marinizers the long block and then they spec'ed and/or installed the rest of the components.

I should have said height, not timing. I managed a large Hatteras Motoryacht for many years with 12v71 TI's (covingtons) and it used a 1.46" injector timing for the injectors it had. Both RPM diesel and Western Branch set up the injectors to the Detroit Diesel injector marine book setting (1.96 or 1.98") I forget which and the engines would black smoke like crazy, I mean like crazy. RPM did it when the buyer had a survey/seatrial and had them compression tested. Then years later Western Branch did it after a major on one engine. The 1.46" injector setting is in the marine book with these injectors but for a generator, not in a propulsion setting. I don't know if Covington set these motors up with an advanced or retarded camshaft setting also, used a different rocker arm ratio, or what, or why they wouldn't run correctly with the proper injector height book setting, but that's how it was and they ran perfect and perfectly clean with the 1.46" setting. But set at 1.98" if you gave them any acceleration at all they would smoke out an entire marina.

Some of the weirdest 92 marinizings out there were the Bivens 92's where they even went as far as changing stroke and other internal items.

These are the kind of blanket statements you enjoy posting and are difficult to understand.

Do you mean lifespan, i.e., useful life of the block or are you back to talking about TBO's? Saying a Covington or S&S 671N gets longer "lifespan" than a J&T is just a bunch of hogwash. There are too many installation/application/care and use factors that can not be accounted for. I know the J&T 671N had a great run in pleasure craft and were noted for "long life" and held their own against the other DD conversions.

Most 6-71 N's are generally known for going 10,000-20,000 hours before a major overhaul. 4700 hours for a 6-71 Natural before a major overhaul is very premature. Those hours for a major overhaul are even a bit low for a 6-71 TI to go before a major overhaul. The J+T 6-71 Naturals used larger injectors and a higher WOT RPM than their competitors. The J+T marinized D.D.'s are well known throughout the industry for using the largest injectors for the same size engine and largest turbo's compared to other marinizers. More fuel, more HP, equal a shorter life in the same engine.

Yes, when Penske bought D.D. he stopped the marinizers from changing the engine setups (injectors/turbo's etc.) and they were marinized in-house. DDEC III can be tuned by a dealer with the factory laptop, although doing so would've voided the engine warranty. Also various DDEC engines ECM's were tuned differently at the factory depending on what vessel they were going in and what propulsion system.

For example, engines slated for Arneson boats had different parameters changed at the D.D. factory in the computer, such as the load lockout removed where if the computer sees over 40% load under 1000 rpm's it will put the computer/engine in safe mode and limit rpm's. There were a bunch of D.D. computer tunes, and if the dealer wants to reflash an ECM the engine serial number needs to be put into the D.D. mainframe to pull out the factory tune for that motor. I just went round and round with this with Sturdy/D.D./and the best Arneson prop guy around on an Arneson boat that had no throttle sometimes and performance issues.

Penske's move created more revenue for DD. It consolidated the dealers to buy one version and generate more in-house revenue for the factory.

The distributors had their regions and J&T had many boatbuilders in the Northeast at the time , Covington in the Carolina's, S&S in the Gulf. But it was common for them to cross sell in different territories, another thing that Penske put a stop to for the most part. But you are wrong to single out J&T as having shorter life amongst the other dealers as you don't know have the all the facts in place.

A J&T 6-71N rated at 310hp vs Covington or S&S 6-71N rated at 310hp and the J&T has lower life - just not true. Same thing for the 6-71TI rated at 410 hp. Keep the comparisons apples to apples.

And you bring back the mythical 41 Viking with 8V-92's again. As I asked before in another thread, prove that that boat was set up by Viking with that power, you never have when I asked before?

Where did I bring up the 41' Viking in this thread? But, the boat was a 41' Viking 1987 or 1988, it used to sit in Brielle, NJ in the summer then Pompano Beach/Ft. Lauderdale in the winter. Same owner since new until last I ran into him was about 5 years ago. The name of the boat was Therapy. I haven't run into the owner in 5 years but used to know him fairly well, however not sure he even has the boat anymore as he is getting pretty old, and not sure how I could "verify" it for you. It used to sit for many years at Sands Harbor Marina in the winter and then the owner bought a condo down the street/canal from Lauderdale Marina about 10 years ago or so and moved it behind the condo. Perhaps you can call Viking and verify it. Boat was the 1 stateroom model with large salon if I remember correctly.

Generally J+T's 71 and 92 series TI or TIB or TAB's were always rated higher and pushed more HP out of the d.d.'s they marinized than their competitors and almost always had the largest injectors and turbo's. I dealt with one boat that J+T stuffed 160 injectors into 12v92's instead of the normal 140's. As for 6-71's most of the turbo'd versions that J&T marinized were 450, 465, and even a 485hp version compared to everyone elses 410hp version. And, generally J+T's lived the shortest lifespan. Yes comparing apples to apples they'd live the same but generally most of the engines J+T marinized they were hot-rodded the most and more than anyone else. Just google it, or search listings of 1985-1995 sportfish and look at the HP ratings.

YO HO ! been cruising this site looking for some of you guys with the Detroit Diesel know how...Sounds like I have found it. I know I am off topic sort of , but was hoping one of you guys could answer a question. I just bought a Post 46 with Detroit Marinized 6-92s , 550 hp ( 1993 ). No real history on them , one may have had a rebuild , alittle quieter and no black smoke when jump on the sticks. I may be right out of my mind but I have this idea to buy 2 6-92s which were in a pair of fire trucks , probably 4 K for the 2 of them .I would strip them of all the road ready gear and clean them up and have them as drop ins incase I suffer a great failier of one of the boat engines. I Wonder if with adding the right injectors , turbo , cooling system , setting up the heads etc if they will basically be what is in the boat. Thanks in advance....

WOW
Before we spend your money, lets review a few things.
The marine 92s may have used up to 4 different pistons in the marine application. Have no idea what piston was in a fire truck.
Exhaust manifolds and turbos are not compatible.
The marine 92s used 2 different gear driven blower speeds. Have no idea what ratio was in a firetruck.
The marine 92s used a whole bunch of different injectors. Have no idea what was in a fire truck.
The marine 92 may have advanced cam timing (usally big HP). Have no idea what the cam timing or hp is in a fire truck.
SAE 0 and 1 bell housings were used in boats. Different fly wheels. Different harmonic ballancers. Different oil pans, oil pumps, oil coolers.

For your purchase and storage waiting for the big one to happen, it may be smarter to put that cash in a savings account, don't touch it ever until you blow up an engine. Storage will be cheaper.

I have considered the same thing for my 12v71TIs. I spent the money on rum and fuel. I'm still ahead.

,rc