Detroit Diesel 71 series engines

Sun, interesting to hear the Industrial side of the story and the fuel burn delta.

There have been a number of boats that have attracted me that were powered by DDs. I note that many of them have been rebuilt at around 2K hours. That scared me off.
Then a very close friend with a 63' boat powered by 12 cylinder DDs needed rebuilds. One done up north for $64K and the other done down south for $42K. That kind of cost would end my happy home relationship. What am I missing here?

Greetings,
Mr. hm. "What am I missing here?"...





???

For what I read about DD 71, the military version with higher power output were planned for rebuild after 1 or 2 Kh but this was in purpose and because of use and abuse but standard civil version with less power output were more durable. Maybe one of out folk with more knowledge than I have will add info.

L

makobuilders said:

There was an 80ft torpedo retrieval vessel that I nearly purchased years ago. It had two sets of twin 6-71’s to one tranny, but I recall they were end to end, not side by side. [emoji846]

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There was either a hydraulic or electro mechanical clutch between the two inline engines. Those torpedo recovery boats were built before the 12v was available. Later versions had 12v71s.

Natural DDs only have 2 atmospheres in the air box. Can't remember, but the turbo couldn't have had much more than 4. I've never seen a visual oil mist in a DD engineroom, even in my current boat when the mains had 20,000+ hours. I think the air compressor put out the most oil.
In Vietnam the naturals usually went 2-3000 hours. But I saw as little as 1000. I can't remember seeing a turbo DD during that time. I don't think they were out yet. Boats were being operated by 18 to 25 year olds. They operated the boats like they drove cars, flat out. What we called heavies, landing craft with some armor, only made 6 knots when pushed, and got frequent rebuilds. Heavies were WWII steel landing craft that could carry a small tank. Most had 3 manually turned turrets w/ a 50 cal, and some had a helo deck over the hold. In VN the sides were built out about a foot on the sides and rows of rebar, a few inches apart were added and the space filled with a fiberglass "armor". The rebar was to ignite RPGs or anti-tank rounds before they contacted the hull. The fiberglass absorbed much of the blast. But all of it added beam and weight.

Lou_tribal said:

Hello fellow TFers!
While reading another recent thread about engines I started to search info about Detroit Diesel 71 series engines. I am not owning any but reading history and information I was very interested about it (for my own curiosity/education).
I love old engines and I found really interesting the long history of the series and its architecture etc.
Would you have any story/info about these engines please chime in!

L

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The US Coast Guard used a variety of 71 series engines, including 471's for generators and hydro pumps and commonly, 671's in their workboats - 40' search and rescue crafts with twin engines. They were extremely reliable and easy to work on - I was a boat engineer and used to work on them routinely in the early 1970's.

Known affectionately as 'Screaming Jimmies' because of their unique and fairly noisy sound, they are one of the simplest and most reliable diesel engines ever produced.
71 is the number of cubic inches per cylinder, and there is a series of engines (1 through 24 cylinders in straight and V configurations the 16 and 24 cylinder models being 8 and 12 cylinder models bolted together) with a 70% parts interchangeability which is great for keeping parts prices low.
When I was in the South Pacific in the 70's, I saw many WWII era 6/71's still in operation, some operating quite well on less than all cylinders because the Islanders couldn't afford to repair them.
One of the really nice things about them is that one can purchase air starters for them. This precludes the need for batteries and an electric starter and an air starter can be powered by at least 3 methods. 1) A hand pump to get enough air pressure in a tank. 2) An air compressor on the engine keeping a tank full. 3) A scuba tank. So, no matter what, your Jimmy should have enough air to start!

They are fairly heavy for the horsepower they produce, and a bit noisy, but if I had the room and could handle the weight, I wouldn't hesitate to put one on any vessel.
I began commercial fishing the West Coast of the US, from Mexico to Alaska, as a teen and every vessel I ever worked on had a Screaming Jimmy. It wasn't until some years later that Cummins and Cat attempted to enter the market.

I worked on 6-71's as ship power providers as a teen-age Canadian Sea Cadet helping convert a U.S. minesweeper (USS Rhea) into a training vessel in the early 1960's.

She was built in 1942 and served in the Pacific war. It was my introduction to diesel engines for me and I still have the manuals from this time. This was when I fell in love with the sea (although we were on the Great Lakes) and went on to train as an officer in the RCN. The 6-71's were a great education for me and the old salts training me having served in the North Atlantic, Pacific and Mediterranean in WWII swore by the reliability of these engines. These engines went on running into the 90's until the ship having been discarded as a training vessel went into decline and finally sunk. Note: She was a Cyprus wood hull and always maintained her water tightness - a great ship!.

I'm a newbie to this informative forum and my wife and I (retired seniors at 73 with a lot of life and dreams still in us) are educating ourselves on trawler types as we prepare to hopefully make a purchase in the next 6 months of a 35 - 45 ft. boat as we want to do the Loop, explore and live aboard as well, especially during the winter months in the south.

We find it very confusing with so many makes and models available listed on many sites with lots of input.

Lou_tribal said:

Hello fellow TFers!
While reading another recent thread about engines I started to search info about Detroit Diesel 71 series engines. I am not owning any but reading history and information I was very interested about it (for my own curiosity/education).
I love old engines and I found really interesting the long history of the series and its architecture etc.
Would you have any story/info about these engines please chime in!

L

Click to expand...

Had DD's in a few boats. I would never have them again. They require very knowledgeable mechanics to do simple things like final filter replacements. Blow an injector tip because of a microscopic water molecule or dirt and you a have washed out cylinder in a heartbeat. There goes $10 grand to fix one cylinder. Their gph to nm curve can be beat by other 4 cycle motors. The DD's with turbos make a 220 hp a 450 hp. and they wont last.

Having run boats and sold boats (about 700 in my twenty years running a yacht brokerage company) and owned boats with Detroits, most of these threads sound like the conventional wisdom of most folks that I encountered as a yacht broker. Don't get me wrong I owned many Detroit powered boats and I love them, BUT there were several companies that supplied these engines to the pleasure boat builders that did not do a great job of marinizing them. Johnson and Towers, Stewart Stevenson, Covington, Penske all with different versions of the same engines. They began a horsepower race to see who could pump the most power of them. Well it did not end well because they took a good old reliable engine that would last many thousands of hours and shortened the life to 2000 hrs (if you were lucky). Example the original Hp of a 671N was 150 HP and year after year the industry started to squeeze out more HP until they got them up to 485Hp. But probably the worse example was the 8V92, they pushed them up to 750 Hp and they cut the life back to 1500 hrs. These were average hr numbers and then there were rare owners that realized the HP rating of the engine could be tamed by keeping the throttles back (no higher than 2000) and/or under propping them so they would stay just above their top rated RPMs. Knew many owners with 485 Hp 671s that got 5000 hrs between overhauls. Same thing is going on today with most high output marine diesels. Most of them get the HP up to at least equal to their Cu inch displacement . It should be the other way around the Hp output should be about 50% of the Cu In displacement of the engine if you want them to last. What I own now are 375Hp. Cats... Displacement is about 650 Cu In and they are pushing 375 Hp. They eventually killed this engine too when they went to 435 Hp . My next boat will have either Lemans or Perkins (120 Hp or 130Hp)

The big question is where will the NEXT boat engines of 100hp or so come from?

Electronic injection and turbos seem to be gaining in the truck engines , and probably will be sold to the farm or lawn equipment folks soon.

This means very small engines with big turbos to pump HP for only modest periods of time, just as in autos.

Back in the day the car folks could by overhead valve cylinder heads for a model T.

Perhaps a company will create a head with Bosch style injectors and a mechanical fuel injection pump?

Best dream would be a current engine mfg that made the newest version of his engine backwards compliant , so an existing mechanical head and injection would simply be a bolt on.

The entire world , 3rd world to 1st would be a huge willing existing customer base.


***************8

For cruisers the DD rule of thumb for 71 series engines of 20-30HP per cylinder gives a very long life , .

A 6-71 at 1200rpm is a smooth delight, the hot high power engines in sport fish are not a comparison.


With almost any brand of engine 3 cubic inches per cruising HP seem to give really long life.

I had a 40' RV (about 42,000lbs) powered by a 450hp DD92. That engine never let me down and would push the coach effortlessly up long, steep grades. Was contacted over the CB more than once by truckers wanting to know "whatcha got in that thing?" after I flew past them on a grade.

I wouldn't hesitate to own a boat with DDs.

Jdoc said:

During oyster harvesting which accounts for about 80% of the engine hours the engine runs at around 800 rpm. Although I’ve heard so much about how bad low speed operation is on diesels, we never experienced that on the workboats around here with the Detroits.

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Yeah I grew up in Venice on shrimp boats. I just couldn't understand all the hoopla bandied about on boating forums by "knowledgeable" advisors regarding low speed/can't reach rated rpm set-ups are death traps just waiting to swallow the universe. I later deduced that it has to do with having to design pleasure boats for the general public who may wander in to a shop and buy anything their pocketbook can afford with no knowledge of its proper operation or design parameters. There are far more people out there who don't know that a diesel blowing black smoke for longer than acceleration or short bursts of power is BAD than there are who do. Never knew of any commercial fishermen who could afford to run their boats like oilfield skippers did. For them travel time=money. For commercial fishermen, nets in the water time=money. None of them "fish" at "rated" rpms. Since my pleasure boats weren't used commercially I propped them for MY preferred enjoyment (factoring in speed and fuel burn) and always told prospective buyers about this.
Not saying I know everything about marine propulsion, but i do know there is more than one way to "properly" set up a propulsion system. There is a factory recommendation to most safely cover the engine for all applications and operators an engine may encounter, but its not necessarily the best for any one specific use, but they can't tailor installation recommendations to every setting their engine may be used in.
Its kind of like the insanity used in designing the modern US diesel pickups. A large portion are used for nothing more than transporting people, yet they are set-up to be able to deliver massive amounts of power/tq at 70 mph in overdrive because average Joe doesn't know that his vehicle could be set-up to deliver significantly higher MPGs in OD when empty or lightly loaded and that he should drop down a gear or even two when working the vehicle at/near its max payload/tow rating. When Ford/International came out with the Powerstroke ('94~ish) and the aftermarket tuners popped up shortly afterwards I was amazed at all the people blowing engines and burning up transmissions in these big sportstrucks! They thought it was so kewl to be able to roll coal and do burnouts till the tires popped. Problem was the tuner companies didn't know much more about diesel characteristics than the new breed of owners did. By the 2000s most of the tuners had developed programs that were much "safer" but that still offered improved performance for the general public. To get the big power programs you had to call and talk to the tuners and acknowledge the need for further parts/modifications to "safely" use these tunes and that the tuners wouldn't be responsible for damage through their use! Of course Ford, Dodge, and GM wouldn't take responsibility for anything if they found a programmer had been installed. Their thought was "We tried our hardest to idiot proof these things and damned if they didn't make smarter idiots!"

I've worked on these engines most of my life, not so much in recent years, and although they are not the most fuel efficient diesels compared to current electronic engines, they are incredible engines, as per many comments above, and there are hundreds of thousands of them in service every day in just this country, and many many more across the planet.
I actually have a HYDRAULIC TEST UNIT, made to opps check F-16s and others without the need to run the aircraft, that is powered by a 6V-53 DD.

I'm actually hoping to sell the unit to someone planning to power a boat, probably a sternwheeler, with hydraulic drive... I only has 164 hours since new and delivers up to 70 GPM at 3000 PSI and is rated to work up to 5000 PSI, via two variable displacement axial piston pumps.

I list this info not only to point out one of the many many thousands of applications but also just in case someone might know someone that is in need of it.
BTW:If anyone is interested, contact me for all info and pics. I'm able to sell this unit at an extremely reasonable price.

I fell in love with them as a teenager while working on a commercial fishing boat. Listening to a 12V71 lug away day and night. I began collecting them soon after, realizing they were going to begin disappearing. My current collection.
2-71 Lincoln welder
2-53 Hobart welder
2-53 440 John Deere crawler
3-71 Sawmill power unit
4-71 Champion Grader
4-53 667 Clark Skidder
4-53 1948 Mack S45
Haven't found the right trawler yet. But I'm hoping that will be the next DD on the list.
They are truly amazing engines and to me as well, the history is incredible.

Justin

Lou_tribal said:

Would you have any story/info about these engines please chime in!

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OK.
I worked on a navy tug in Adak, AK in the 1970s. Two 6-71 generators, one 6-71 fire pump (really big pump!), one Fairbanks Morse 38D8-1/8 main engine.

The procedure for a SAR call was:
1. Run frantically across the parking lot, up the dock, down the brow, across the barge, into the boat and slide down the rails into the engine room.
2. Start one generator. Never any suspense in this step. Generally running 10 seconds after alighting in the engine room.
3. Line up the lube oil valves, start the lube oil pump, and attempt to start the main engine. Shoot ether into a port on the side of the engine first if the weather is really cold.
4. Sync the generator and disconnect shore power.
5. Cast off - objective is two minutes from the initial call. Easy if we were already on the boat, possible if we were in the building, usually more like five minutes if we were in bed.

Of course we always kept the starting air cylinder and day tank full.

I read that some think the 6-71 is noisy. They haven't heard a 38D8-1/8.

Reading all of your experiences and comment is a real pleasure. Please keep them coming.
I do not own one but am really interested. I like reading old engines manuals very much (this sound a bit bizarre) and this one looked really something to me.

L

Having worked at a Detroit Diesel (when there was such a thing) Distributor, for the first 13 years of my career before switching to the dark side at the EMD Distributor for the last 10 years, and all in the service department, I can say I have seen a few 71's...also 53's, 92's, 149's, Cleveland Diesels (also two-stroke) and of course the "big" GM diesels (EMD) in 567,645 and 710 displacements. And yes, I have repaired a few 4-strokes along the way...the Series 60 brought DD back from the brink in the truck market!

I still have yet to touch the 51 and 110 series Detroits, but that's a story for another day.

As far as the 71 (and other two-cycle diesels go) the Natural Aspirated versions are quite reliable, if inefficient on fuel. However, consider that when they were originally designed diesel fuel was cheap, it was a byproduct!

Regarding the weight of the Detroit's I have seen it proved true many times that mass=durability. The heavy, basic 71 block is a liability in a lightweight planing hull, but in a displacement hull the weight is inconsequential and the ability to run 40K hours without overhaul on a small engine pays for itself many times over.

An advantage of a 2-cycle uniflow-scavenged design for any boat is that you get more firing pulses per crankshaft revolution, (though at a shorter effective stroke) which means they feel "faster" coming up to turns. The downside of the shorter effective stroke is that they are "dragged down" easier - i.e. when running uphill in heavy seas.

One of the nicest things I have liked about these engines over the years are the unitized injectors, which make it easy to service and repair fuel systems without special tools. As well, the ability to remove the airbox covers with a single wrench and inspect cylinders, pistons, and rings visually with no special tools. Regarding the mention that the naturals run 2X atmosphere in the airbox, sorry only 3-5PSIG at rated speed.

One of the biggest problems with the turbocharged Detroits is that they still had to work with the parasitic loss of the blower, even when on boost...though Detroit eventually came out with the Midi and Maxi bypass blowers to help, you still were swinging the iron (actually aluminum) when running at speed. Again, fuel was cheap! Even the turbocharged engines had reasonable life, 24K hours between overhaul if not tuned to "blow up" ratings.

As has been true with many successful products over the years their success was their ultimate demise...too many "certified mechanics", non-OEM parts, wrong parts interchanged, etc. caused degradation of the brand name. Then Detroit didnt help themselves with the barrel-faced rings "there's not a problem" debacle that put the final nail in the oil saturated coffin. The fix did come in eventually, though too little too late, and quitely the 92's soldiered on to Tier I emissions with DDEC III and DPF's in transit service...until the Cummins Salesman came to town.

I won't even mention the scream, earplugs and muffs don't even cut it.

The successor to the 71/92's in at least a few applications was the Series 60, a great little engine that saved Detroit and shared common architecture with the JD Power Tech 13L and Volvo D13, D16...all while still using the Unit Injector design. They did get that part right 80 years ago, now we see it augmented with modern technology in the form of an electromagnetic fuel control solenoid and integrated engine controls!

My OPINION is that there are no "bad" engines, all have their plusses and minuses and it is up to the owner and operator to pick their poison.

Would I run away from a boat with a 2-cycle DD? Of course not.
Would I repower with a 2-cycle DD? of course not! There are many more options today in light-duty engines that make it a tough sell for me to consider installing a 2-cycle DD in a pleasure craft or light-duty commercial or auxiliary service.

And for the record, 2-cycles didn't die with Emissions, there are USEPA Tier IV certified Marine Propulsion and Auxiliary EMD's for sale today.

Follow the link!
https://s7d2.scene7.com/is/content/Caterpillar/CM20170712-52832-51137

Cheers!

Lou_tribal said:

Hello fellow TFers!
While reading another recent thread about engines I started to search info about Detroit Diesel 71 series engines. I am not owning any but reading history and information I was very interested about it (for my own curiosity/education).
I love old engines and I found really interesting the long history of the series and its architecture etc.
Would you have any story/info about these engines please chime in!

L

Click to expand...

I just bought a converted fishing trawler in Sydney and brought her back round the top of Australia to Perth (home) 600 hours and 4 months of pure pleasure and the 8v71 never missed a beat but I did do an oil change every 200 hours

mikeod said:

I just bought a converted fishing trawler in Sydney

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And you didn't show us pictures.

Good stuff. I have enjoyed reading this thread from all of the knowledgeable DD folks.

Spent my time on steam, but can relate to some of the stories including sliding down the rails in to the engine room and landing on steel deck plates. Another reason my knees are shot.

Keep them coming.

Video of Jasmin

FatBear said:

And you didn't show us pictures.

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Here you go ...this is a video of the boat I bought with the 8 v71 in it .. it also shows the engine room

https://youtu.be/cTNfKNr5b_M

I agree with what many others echoed—that The 2 cycle Detroit Diesels were monumental in their impact on the world diesel engine stage. From US tank engines and landing craft in WWII (these new powerful engines undoubtedly helped to win the war!) to the post-war WWII commercial tug and fishing boat re-power upgrades across the US. No other manufacturer can make those claims.

In 1941, (pre-war) My father purchased a brand new 4-71 Gray Marine Diesel 110 HP for a 50 ft oyster lugger. He paid $4000 for the engine. The entire boat finished construction cost him $4000. The power/weight factor was a huge upgrade. At that time most fishing boats had heavy Fairbanks Morse or Atlas Imperial engines 20-40 HP. He said at that time he could have bought almost new Fairbanks Morse for $1000.

After WWII, in (1946 onward) the war surplus of DD’s was so great that they were purchasing 6-71 (165 HP) Gray Marine engines with Twin Disc gears for $1500. That obviously affected most of the US marine fleet.

twiisted71 said:

Yeah I grew up in Venice on shrimp boats. I just couldn't understand all the hoopla bandied about on boating forums by "knowledgeable" advisors regarding low speed/can't reach rated rpm set-ups are death traps just waiting to swallow the universe. I later deduced that it has to do with having to design pleasure boats for the general public who may wander in to a shop and buy anything their pocketbook can afford with no knowledge of its proper operation or design parameters. There are far more people out there who don't know that a diesel blowing black smoke for longer than acceleration or short bursts of power is BAD than there are who do. Never knew of any commercial fishermen who could afford to run their boats like oilfield skippers did. For them travel time=money. For commercial fishermen, nets in the water time=money. None of them "fish" at "rated" rpms. Since my pleasure boats weren't used commercially I propped them for MY preferred enjoyment (factoring in speed and fuel burn) and always told prospective buyers about this.

Not saying I know everything about marine propulsion, but i do know there is more than one way to "properly" set up a propulsion system. There is a factory recommendation to most safely cover the engine for all applications and operators an engine may encounter, but its not necessarily the best for any one specific use, but they can't tailor installation recommendations to every setting their engine may be used in.

Its kind of like the insanity used in designing the modern US diesel pickups. A large portion are used for nothing more than transporting people, yet they are set-up to be able to deliver massive amounts of power/tq at 70 mph in overdrive because average Joe doesn't know that his vehicle could be set-up to deliver significantly higher MPGs in OD when empty or lightly loaded and that he should drop down a gear or even two when working the vehicle at/near its max payload/tow rating. When Ford/International came out with the Powerstroke ('94~ish) and the aftermarket tuners popped up shortly afterwards I was amazed at all the people blowing engines and burning up transmissions in these big sportstrucks! They thought it was so kewl to be able to roll coal and do burnouts till the tires popped. Problem was the tuner companies didn't know much more about diesel characteristics than the new breed of owners did. By the 2000s most of the tuners had developed programs that were much "safer" but that still offered improved performance for the general public. To get the big power programs you had to call and talk to the tuners and acknowledge the need for further parts/modifications to "safely" use these tunes and that the tuners wouldn't be responsible for damage through their use! Of course Ford, Dodge, and GM wouldn't take responsibility for anything if they found a programmer had been installed. Their thought was "We tried our hardest to idiot proof these things and damned if they didn't make smarter idiots!"

Click to expand...

Yes, all the Detroit marine diesel mechanics I’ve ever talked to said you should run them at their maximum designed rated rpm (1800 or 2100 for NAs). This, of course is good for them, the mechanics, because pushing a marine diesel engine hard gives them more work. It is common to get a 1000-2000 hr life used in crewboats running wide open, vs 10,000-20,000 hr life in fishing boats when run at 1/2 to 2/3 HP ratings.

We have an 871 as our main engine and a 353 as our auxiliary for hydraulics etc.
I bought the boat as Neptune's Chariot in 2011 with 22,500 hours on the 871 (built in 1981) and against Larry Briggs the previous owner's advice I required he do a rebuild before I took ownership so I had a line in the sand as to where it was mechanically.
We stripped it down in hull and rebuilt it. I needn't have bothered - it was still in great shape. We have since done another 4,500 hours without missing a beat, even during a fuel bug drama.
We have good sound proofing so the noise is not an issue and I love that "solid" reliable comforting sound.
We have always run it at 1600RPM but Larry told me he ran it mostly at 1900RPM until the last 5 years he owned her because fuel cost was not an issue back in the day.
The boat now MV LOST in ASIA is also surprisingly good on fuel - we use only 23 Ltrs an hour at 1600RPM = 9.2Knots in our 75' x 110 Tonne full displacement motor yacht.
Larry liked to fuel up and go so she had over 11,000 gallon capacity when I bought her = 13,000NM range at 9knots.
He did 2 circumnavigations and a number of trips across the pacific in her and I loved his stories and anecdotes before he passed away 5 years ago.
I have since converted the 2 x 1000 gallon aft tanks into fresh water tanks and removed the old aluminium water tanks from the lazarette making heaps more storage area and reducing the range to "only" around 10,000 NM.
One thing Larry instilled in me is to achieve long life on DD's you must change the oil every 200 hours and the filters every second oil change which is why we have a 100 gallon oil tank on board above the engine. We also add the used oil to the 800 gallon "day Tank" and burn it.
I could not speak more highly of these engines, but like everything - you either love them or hate them.

mikeod said:

I just bought a converted fishing trawler in Sydney and brought her back round the top of Australia to Perth (home) 600 hours and 4 months of pure pleasure

Click to expand...

Pictures and a story or it didn't happen.

Just saw the vid, nice.

My brother just bought a vessel with twin 16V92s. Parts are still easy to come by, it is the mechanics to do the work that becomes the challenge. Most of these guys are greybeards and the new guys are getting training on the Series 60s and other 4 strokes. Moral of the story, treat a good DD 2 stroke mechanic very nicely.

The WWII Grey Marine military repair manual is almost like reading an adventure book!

It covers the engine design , boats installed in and minor to major overhauls . EVERYTHING!

For a 6-71 owner there is no finer handbook.

Totally enjoyable is the parts list of parts price$ at that time.

There are many , here is an example to download.

http://www.cg83527.org/DD671Manual.htm

Lou_tribal said:

I read that the last 71 series engine was delivered in the 90s, this is a heck of a longevity for an engine that started to be built in the 30s!

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Not sure about the 53 or 92 series, but I hear tell that parts for the 71 series are going to remain available through the year 2045.

Very well said pacopico...

pacopico said:

Having worked at a Detroit Diesel (when there was such a thing) Distributor, for the first 13 years of my career before switching to the dark side at the EMD Distributor for the last 10 years, and all in the service department, I can say I have seen a few 71's...also 53's, 92's, 149's, Cleveland Diesels (also two-stroke) and of course the "big" GM diesels (EMD) in 567,645 and 710 displacements. And yes, I have repaired a few 4-strokes along the way...the Series 60 brought DD back from the brink in the truck market!.......

Cheers!

Click to expand...