Know Your Diesels – The Detroit Diesel Series 71

Welcome to the first in a series of stories relating to famous diesel engines of the past and present.  I can’t think of a better one to start with than the Detroit Diesel Series 71. The story begins back in 1938 when GM subsidary Detroit Diesel unvieled thier first product, the two stroke, inline 6 cylinder 6-71. The inline models were offered in a one, two, three, four and six cylinder variants. In 1957 V-block versions were introduced and would eventually included 6,8,12,16,24 configurations. At first glance the naming convention seems cryptic but is rather straight forward when you think about it. For example, the 6-71. The six stands for the number of cylinders, the 71 stands for the cubic displacement of each cylinder. The 12V71 is a 12 cylinder in a V-block setup. To continue the code a T would stand for turbo charged. L or N would stand for low profile, a setup commonly used in buses. The larger of the 71 series in a V-Block configuration were usually two of the smaller setups married together our used the same set of heads allowing parts to be easily swapped. The applications of the 71 series were limitless. 6V-71 were common with bus and coach builders. 8V-71 were popular with firetruck manufactures, it is pretty difficult to find an old fire truck without an Detroit under the hood or cab. But to really appreciated a Detroit you have to hear it, they truly have a sound all their own. So, on to the videos.

6-71 – 190 HP

12V71 – 450 HP

8V-71 – 318 HP

I hope you enjoyed my novice homage to this great and long lived engine. Despite their unfailing ability to constantly leak oil you will still find fans of the 71 all across the globe. Please feel free to correct or and any relevant information by emailing eric@dailydieseldose.com or just leave a comment below. If you have a candidate for the next KYD story let me know!

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80 Responses to Know Your Diesels – The Detroit Diesel Series 71

  1. Pingback: The Worlds Fastest Truck |

  2. Tim Henshaw says:

    In my mind one of the best engines every made. Not the most powerful, but what other engine has lastest the test of time like this one.

    Love those Rocky Mountain Hummingbirds!

  3. willie kemp says:

    my question,I have a 6v71 lh rotation eng I am a mechanic too and want to change it to rh I know how to do this but am wondering if the cam shafts are the same

    • Rupert Penjab says:

      The cams are different between the lh aha rh versions. If you ever tried to stop one of these engines by stalling it you know they will run in reverse, but the power isn’t right, you have to change the camshaft.

    • Dick Hoover says:

      I was told by a mechanic that the same camshaft was used for either rotation; it had to be removed and turned end for end. Not the same for the starter, you will need one with the correct rotation.

    • Tom Brownell says:

      I had a Detroit in a loader and had to swap engines because the engine went bad. I ordered a military engine from boats and harbors with an opposite rotation. All I had to do was in bolt everything from the block and rebolt it on the other side of the block and reinstall the engine. In other words just turn the block around. The engine is symetical, so it all bolts back up when the block is turned around.

    • Angel says:

      No they are not the same there are RH and LH camshafts

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    I am going to recommend this blog!

  5. Roy Kennedy says:

    Before GM made Detroit Diesels in V configuration, they married two or four 6-71’s together in”twin” or “quad” installations. I remember seeing two quad installations in the engine room of an ex US Navy inshore minesweeper. Imagine the glorious howl of two 24 cylinder powerplants at full throttle. Makes my spine shiver! I worked on boats with 6-71 and 4-71 engines. No matter how many cylinders, they all sounded the same to me, a nice throaty rumble at idling speed that became a uniquely soul stirring scream at 1800 rpm. Wonderful.

    • Rupert Penjab says:

      You certainly did not walk around anywhere near the air intake with an oilers rag in your pocket.

      • Owen F. McCaffrey says:

        I sniped a bunch of LCVPs, Mike6 boats, and Captain’s Gigs as an engineman in the U.S. Navy from 1973-1977. Motor Whale Boats too (Perkins powered). I became really proficient at trouble shooting and rebuilding Jimmies. It was my passion at the time. I used to rebuild and pop test the injectors as well. In addition, I also operated, maintained, and took part in rebuilding one of our Fairbanks-Morse emergency generators aboard USS Coronado LPD-11. Later in life I used to drive a 238 powered White 4000 single axle tractor with a 10 sp. Roadranger pulling tank trailers. Love the Detroit 2 cycle sound! By the way…the are made to run up to 2,100 rpm. Typical operation. Thanks for the memories!

        • Jim says:

          Owen F McCaffrey….. “By the way…the are made to run up to 2,100 rpm.”….. just so you know, the series 71 engines “can” be taken up to well over 3,000 rpms.

          We ran the v12 in the Kenworth that we ran in the Pro Semi Class of Sled Pulling at up to 4,200 rpm and never blew it up, in nearly 32 years of pulling, though did spin a bearing once.

  6. Roy Kennedy says:

    Further to my previous comment, I remember a pair of “handed” Gray Marine 6-71 engines, with Twin Disc marine gearboxes (Allison Division of GM) that had been taken from a landing craft, so they had been built during WW II. They still had their brass plates on the flywheel housing with the official number issued by the US Bureau of Ships. They had the larger injectors, and when the boat was fresh out of refit, they could push her along pretty smartly. We used to run up to 1500 rpm, but could push 1750 if needed. The biggest trouble was keeping the seawater cooling system clear of weed and mud which could cause overheating. The boat was eventually scrapped, but I don’t know if the jimmies survived.

    • Eric says:

      Unless someone was foolish enough to junk them I bet they are still running!

    • Owen F. McCaffrey says:

      That’s so true Roy. As I remember (it was many years ago) you had a sea water strainer before the keel cooler you had to keep clear. The Jabsco pump did not like to run dry. We used to pack the rubber impeller with grease to lubricate them until they picked up salt water. It was just a half-dozen Phillip’s head screws to get the cover off. I would do it again! Sometimes the bosun’s mates would let me drive the boat (Mike 6 or LCVPs) I got pretty good at it! I even landed 80 or so drunk Marines up against the ship. They all were laughing and taunting me. I made a smooth docking. We used to cook misappropriated Marine C-rats on the exhaust manifolds. I even steered an LCVP drive by of a Russian cruiser off Cypress one time! All done with Gray Marines. Good times.

    • Jim says:

      Roy Kennedy….. “We used to run up to 1500 rpm, but could push 1750 if needed.” It’s a wonder those poor engines survived at such low rpms…. None of my Detroits ever saw less than 1900 once under way…. with the governors set for 2,850 rpms… loaded.

      Most all “pleasure craft” detroits came from the factory set at 2,350 for the Series 71 engines. In the Pro “Sled Pulls” for Pro-Semi Class, we turned the V12 (71 series) at 4,100 to 4,200 under full load for years, and never blew it up.

  7. Charles Jarvis says:

    While in the US Navy I was in Viet Nam on lcu boats. There was 6 engines on each boat, three 6-71’s for power; two 2-71’s for electric power and one 4-71 for the anchor winch. The engines just ran and ran. We had injector problems because of dirty fuel, so injectors was replaced frequently. The 6-71’s turned a 4 foot 4 blade prop, engine ran at 1600 rpm’s. A few times ( in time of need ) would be pushed to 1800 rpm’s. One day we blew an engine ( actually the twin disc clutch ), Pieces was every where.
    Always liked the sound of the engines running at cruising speed ( 1600 rpm ). One class of boats had a pair of 6-71 together on one shaft, one right hand rotation and one left hand rotation, I think they was turbo charged units These boats had two shafts. Very dependable engines all the time, as long as the fuel was good and oil was maintained. Charlie J.

    • Owen F. McCaffrey says:

      Thanks for serving Charles! Great story appreciated by this former Navy boat snipe. I sure do remember those twin discs.

  8. Hawse Pipe says:

    I have 12, 8, 6 & 4 V-71 detroits firing both my fleet of tugboats and workboats as well as a few cranes and dredge pumps.

    They are all Naturals and I simply love them. Not much is reliable in this world and at sea I have learned that I can count on only 2 things.

    1.) Without fail the sea will be relentless and when it bears its teeth there is absolutely no room for error or hesitation, particularly in the engine room.
    2.) My Detroits will never stop running and will dig deep to power through anything the sea throws my way. The only reason they will stop running is because I have safely returned to port and shut them down.

  9. Out of the million miles or so I drove 18 wheelers across the lower 48 many years ago, I must have around 400,000 miles in a Freightliner with a 8V71. They were commonly called 318s back then also. That was the horsepower rating with a specific injector size, mine had 290s. The transmission was a two stick 4×4, a Spicer, I think. It was the best designed of the two stick transmissions I had experience with.

    All the Detroit two cycle diesels had what is called a ‘roots blower,’ a mechanically driven supercharger with two spiral, intermeshing, rotating lobed shafts that compress air. They were a basic part of the design and I doubt the motors would run without them.

    Mack engines commonly had turbochargers back then. Later on turbos were paired with aftercoolers and the power really began climbing.

    • jay dee says:

      I own a 1959 GMC 860 short nose cab over hosting a 6-71 DD coupled to a 5&2. I love everything about my truck. He’s a grumbly looking ugly mutt that musters up one hell of a racket anything over idle. Yessir, my truck: all the right parts in all the right places. I love my truck oh yeah!

    • JohnW says:

      6-71 blowers only served to push air thru the two stroke intake ports.

      Because the exhaust valves were still open when the piston covers the intake ports in the cylinder wall.

      The blower was used to “scavenge” out the exhaust gases.

      Not until a turbo was added did the over pressure help rise horsepower. The roots blower didn’t boost intake pressure over a naturally aspirated engine…

      • Jim says:

        JohnW…… “The roots blower didn’t boost intake pressure over a naturally aspirated engine…”. Not sure where you got that idea from, however…. an NA (Naturally Aspirated) Detroit IS Roots equipped, and when the engine is “fresh” there IS about 3.4 to 4lbs of “boost” over atmospheric… depending on altitude, humidity, etc.
        There is no such thing as a “naturally aspirated” 2 cycle GM Diesel (Detroit Diesel after mid 1965) without a Roots Blower, they cannot run without it… as the governor is also driven from the blower, as well as the fuel pump in many of the different models, though there were a Few which the pump was run off of the rear gear drive.

  10. Brett Hughes says:

    These engines seem to get everywhere. The first time I saw and heard one of these was in 1983 in the technical collage I was attending in England. A yellow 6V-71 with a Roots Blower sat on top. It was on a test bench and I could hardly hear the engine over the sound of the blower.

  11. alex putman says:

    my dad has a tug boat with 2 1983 6L-7 1s and the port one blow up but still run hard to start will run (try that with a cummins) it blow up because the port water pump broke (i think it was made by cummins) i am only 14 and detroits may be befor my time but they are still the best

  12. Rupert Penjab says:

    The Fire truck manufacturers really preferred the 53 series Detroit engines…….. it made for an interchangeable gas/diesel application as the 53 series is a near interchange for a gasoline engine and didn’t require gear ratio modifications.

    • Jim says:

      Rupert Penjab…… Not sure where you got that from, however… more than 70% of all 2 cycle Detroit powered fire trucks were Series 71 powered…. there were a few of the smaller trucks that were 6V53 powered, but not many compared to all the 71 series over the decades.
      As far as the “inter-change” part of your comment… yes, the 53 series could be had with either an SAE no.3 or no.2 bell housing which would make it pretty easy to convert from gas power to diesel… especially with a no.3 bell housing if in a smaller truck.

      • Paul says:

        THIS!!! In over 30tears never encountered 53 series in a class 8 fire apparatus; 6-71 in Pumps and 8V71 or 6V92 in Ladders

  13. frank oruene says:

    observe high temperature on a 8v 71 detroit diesel radiator and fan cooling, ive flush radiator but temperature is still high

  14. Chelsey says:

    Hey Everyone!
    I have a question about GM detroit diesel 3-71 marine engine. I am unsure of a couple of things about how to service this engine. I am looking for some helpful knowledge.
    We have change the oil for the marine gear but don’t know where to fill up the oil fo the engine oil….? We have located an oil strainer but arent 100% sure if this is the fill in port? Any help would be much appriciated. There aren’t alot of helpful forums out there so im hoping someone in here can help me out!

    Cheers!

  15. Crabber50 says:

    I have two 6-71TIB’s in my boat and absolutely love them, the more I learn about them the more I love them. Really appreciate all the comments, love to the history. Thanks for your stories and service.

  16. Todd says:

    I have a 671 in my 1955 FLEX VL 100 tour bus. Jake breaks and Alison Transmission. What a blast to drive. I love the sound. I worry if I ever need a mechanic, I will never find one who can work on this old power house. Costa Mesa Cali.

    • Eric says:

      Hopefully that day never comes. The 6-71 has been around for almost ever. Lets hope a few from the next generation learn a thing or two about them.

  17. Tom Christman says:

    The bore and stroke on the 71 series is 4.5″ x 5″. They stopped making the 2 stroke Detroits in 1998 (they still make the 6V-53TI, 8V-71TA and 8V-92TA for military vehicles). It is interesting to note that the 2 strokers were cancelled because of being dirty burning and couldn’t be cleaned up to smog standards.
    Yet the largest and most fuel efficient engine is a 2 stroke made by various companies. The largest has a 39″ bore x 135″ stroke (yes that’s 3″ over 11ft!). They power the big container ships and by cross section, look like big versions of Detroits.

    • Jim says:

      Tom Christman…… Tom, just so you know, the 8V71T & TA is no longer available “new”….. the military orders dropped them.

      There are Numerous large 2 cycle diesel engines and engine builders around the world…. not just “a 2 stroke made by various companies.” The Biggest that you were referring to is the Wartzila-Sulzer RT96A & C… originally designed by Sulzer before the merger with Wartzila from Poland. There are Many 2 cycle diesel builders in the world, including Fairbanks Morse from the US who have been around since quite a while before GM Diesel or EMD… originally since 1823…. before they (FM) started producing engines, actually.

  18. Todd says:

    671
    Does anyone know where to fill the transmission fluid? Theres a canister above the tranny on the very back of the engine.
    Thank you,

  19. Drew Hall says:

    I need your help or that of any diesel mechanic you may happen to know.
    The all-steel 1940 former Baltimore City Police Patrol Boat CHARLES D. GAITHER supports a Detroit 671 diesel engine in her spacious engine room. Can anyone date the engine by its serial number of 6718454. It has a five-pointed star following the number and we were wondering if this signifies it as being original, rebuilt or something entirely different. If it is the original engine, most likely it was manufactured between 1938 and early 1940 just prior to when the vessel was launched. Can anyone possibly give us more information about serial number 6718454 (star) Thanks.

    • Eric says:

      Drew, I would be interested in hearing more about the history of this boat. If you can send in a photo or two along with any interesting details I’ll put together a post that hopefully will be seen by more eyeballs. Email eric@dailydieseldose.com

    • Jim says:

      Drew Hall…. Hi Drew, you’ve probably long since gotten your answer… I just found this great blog.
      What I can tell you is that for sure it would have been between 1939 & 1940, as the engines did Not go into production until 1939. I know this because I formally studied Engine design for four years back in the early/mid 1960’s and three of those years were under Pat N. who was one of the principle designers of the original Series 71, directly under “Boss” Kettering.

      By the way… contrary to popular “myth”…. the Very First Series 71 built was NOT a 6-71… it was a 4-71 and I have an 8×10 of it taken just after its first start up, with Kettering, Pat and a 3rd R&D engineer whom I’ve forgotten the name of at the moment…. but I have the picture hanging righ over my desk here, which was given to me by Pat after I returned from VN in 1970.

      Back to your question regarding the Serial Number…. I’m not sure where you got the number your showing but it sure doesn’t look like any Serial number I’ve ever seen for a 6-71…. it should start with (ie:) 06Axxxxxxx.

      Also… I can tell you more about the engine from it’s model number, than its Serial number…. everything except the date. Can you give me the Model Number…. AND the Serial Number from the Machined pad…. located in my decription below?

      OK…. a couple of questions for you, Where on the engine did you get this number? Off the “tag” on the rocker cover? The “star” you mention is Definitely NOT from the factory. There are TWO locations for the Serial AND Model numbers….. one of them is “incorruptable” (unless somebody bothered to grind it off – literally), and it is found on a machined “boss/pad” which, when FACING the Front of the engine – from the Front…. will be on your Left hand side of the block directly BELOW the top of the Block “deck” where the head and head gasket meet the Block…. and the machined “pad” with the Serial Number – followed by the Model number (below the serial number – on the pad) is just behind the very Front of the engine Block.

      This machined “ID” pad was common to ALL Series 71 INLINE engines from One to Six cylinders.

      The other location is the metal “tag” mounted on the rocker cover, of course.

      Question…. is the rocker cover Stamped Steel with “knob” style hold-down bolts through the cover….. or, is it a Cast Cover with “DETROIT DIESEL” in Raised letters on the “angled” portion of the cover between the very top & sides of the cover?

      Next question….. look on the sides of the block (either or both) towards the lower portion of the block….. does it have an “arrowed” circle with Detroit Diesel embossed & raised in the block – Or – does it have a raised or embossed “Rectangular box” with GM Diesel Power (with the GM in Large Caps at the top- Over the words Diesel Power in smaller letters and Diesel Power, one over the other) “in” the box?

      The “heat exchanger” box at the top and front of the engine “could” say GM Diesel Power, Detroit Diesel or Gray Marine…. any of the three are “telling” for different reasons…. but, in trying to ID the engine…. the most important numbers and letters to me, are located at the location I pointed out to you… On the BLOCK….. NOT the rocker cover.

      One more question….. do you know if has a 2 valve or a 4 valve head on it?

      I cannot say for sure about the “star”…. but I’ve never seen one in relation to the Serial number…. but not to say they didn’t… but, again…. look at the numbers on the “pad” on the very Left Front of the engine block and IF you don’t see a “star” there, preceded by the serial number… then “someone” else stamped it – and probably during a rebuild (or a reman, possibly?).

      Did you buy this historical old police boat? Good luck with it.

  20. crazy mike says:

    i have a 83 white road boss with a running 671t in it right now with a hole in the block, no oil in motor or coolant, connecting rod smackin around and starts up in the pa. winters !!!!!! no bs. Awesome engine!!! try that with todays crap.

  21. Andrew King says:

    The most reliable diesel ever built. The best sounding engine is the 6-71 and 8V71
    natural in a truck fully loaded going up a grade. They go a lot better with a turbo and more economical but the sound changes. I want to buy an early 1980’s R600 Mack
    bogie with a slightly extended chassis and stick a 318 or 6V92T in it and a 48 inch sleeper. Rt0 9513 Alcoa wheels on the front. I’m from Brisbane Australia.

  22. Mike says:

    Best diesel for sawmills an some trucks they will run for ever

  23. Adair James says:

    my field service book says Detroit made 568 inline 24 cylinder 71’sne seen one

    • Bill Barsby says:

      I won’t think that there would be an inline 24 cyl. The V16-71 was two V8-71’s bolted end to end so I would the that the 24-71 would be two V12-71’s bolted end to end the same as the V16’s. I have never seen one though I have seen 16-71’s though.

    • Mike P says:

      There would be a cylinder firing every 15 degrees… That would be SMOOTH.

  24. Bill Barsby says:

    Years ago I had a 125kw gen set powered by a V671 . It ran at a constant 1800 rpm. I never leaked a drop of oil and was the only diesel that I have ever seen that the oil was the same colour going in as when it was changed. That oil never got black. They ate great engines.

  25. Kevin Dutchers says:

    Any idea what a 6-71-based design could be pushed to, hp wise, with modern metals, rings, bearings, etc and not worrying about emissions?

  26. Dayne says:

    My company dismantles and parts out old Euclid and Terex off road haul trucks. We still get to play with these engines almost everyday. Such a great sound!!

  27. Al Lindner says:

    I miss the old 2 cycle Detroits, very reliable and parts were inexpensive compared to Cat or Cummins. The ’71 series were great, the ’53 series were junk, also the ‘149 series were excellent as well. Shame they are no longer in production.

  28. Robert Cates says:

    Im looking at a boat with GM 4-71-TI’s with 6000 hours. What What I’ve read is they last a Long time but are they at a point of needing replacement or overhaul. Thanks for any help

  29. bob says:

    Just stripped for planned maintenance, a 6-71 ti marine gen-set after 15000hrs work @ 1500rpm (50hz) mostly under heavy load and still has honing marks inside the cylinders!
    Regular oil changes, run warm but not hot and it’ll just keep going.

  30. tyler green says:

    great stories. I might be able to keep this going. I have a 6-71N in my 44′ commercial vessel, keel cooled. Model:6-71RC7 Serial:6713433 still has original stamp plate. local diesel shops tell me she’s an oldie. Runs like a top, sounds like a jet engine at the exhaust. I am having problems finding a specific manual for this ol’ girl. engine temp got to 190 and overflowed coolant out of the expansion tank. I changed out the coolant, flushed the system as best I could and replaced with fresh coolant. Ran it for approx. 15hrs and she got up to 190 again for about 10 min and back to normal operating temp at 180. Next stop is thermostat but it worries me that the system pushed back pressure through the expansion tank. Any thoughts?

  31. John Russell says:

    At mass maritime they still teach the cadets on in 6-71 s, which is great, my boy just went through the class and will rebuild the 4-71 that sits right behind me in the crane I run every day. The work boat has a 6 -71, and the tugs have 12-71, all naturals getting 25000 hours on the tugs mains before overhaul. They may require some skill to get them to run perfect but this old fool can always make em run, good enough.
    Had to get teir 2 motors in a new machine, lots and lots of wires, no tinkering those babies home when they stop that’s that. When you out on the water……..

  32. WJ Cleary says:

    Greetings,
    I have been considering buying a cabin cruser about 35 to 38 feet long but most are gas powered and they really suck it. I would like to talk with anyone who has converted a boat to diesel. I like the thought of the 4 cyl. 71 series Detroit. but have no experience with it other than reading about it any comment?

  33. Kriss says:

    Hi all. I’m looking for a bit of help finding some parts for a 3-71. My plan is to install it in a 1966 Dodge one ton so I’m looking for an automotive governor and a 6V-71 truck exhaust manifold and the bit to hook up the pipe to it.

    Around Seattle you use to be able to find Jimmy parts just about anywhere now it’s good luck!

  34. Fred says:

    What is the weight of a 6V-71 engine.
    Can’t find it online somewhere….

    No cooling, start motor or generators installed.
    I need to put it on a trailer for transportation.

    Fred

  35. Jerald Lamb says:

    I have a customer that ran twin marine 12v71’s out of fuel. I installed new seperator filters, secondary filters, fuel lines, bled the system and both engines fired up immediately. Both run great but after they reach operating temp, 1 stalls out. It will start again only to run a little while then stall again. What is the issue?
    1. Bad fuel pump.
    2. Dirty injectors.
    3. Fuel regulator.
    4. Air intake.
    5. Governor adjustment.
    Thank you.

  36. James says:

    I was in a vo-tech high school back in the 70s and we had a couple of Detroits in the shop. We had a 8-V71 out of a Bus and a 2-71 that they said was off a military generator unit. They were both a joy to work on and to this day I love the sound of a Detroit.

    My buddy, from high school, became a curator for a railroad museum. I was visiting one day and we cranked the big Detroit in an over-the-road, Santa FE war bonnet, a-unit. What a thrill! The valve cover was off and you could watch the rockers slowly moving up and down as the engine spun over. A release of the compression release lever and it came to life.

  37. Randy Ashman says:

    Talking about stalling problems , two marine 12V71 naturals housed in a Mark ‘ll patrol craft fast Swift Boat.
    Both . The port engine stalls eff hen tsken out of gear and put bavk into gear ig stslls why?

    • Jon B says:

      The problem is most likely high fuel pressure due to a plugged restricted fitting or closed valve in the return fuel line or a stuck relief valve in the fuel pump.

  38. Kevin heske says:

    Hi guys
    Is the engine block the same size in a v671 and a v692 ?

    Thanks

    • Jon B says:

      The racks can get bound up and will be unable to keep the engine from stalling at idle due to high fuel pressure. A sticking fuel pump relief valve or a return line restriction i.e., plugged restricted fitting or a valve shut off.

    • Jon B says:

      No, The 6V-71 and the 6V-92 blocks are completely different. The 71 has dry liners and the 92 wet liners.

      • noname says:

        But they are the same size. 8V’s also. You can swap out a 92 for a 71 with no changes in the bodywork … at least on a bus. Been there, doen that.

  39. Wayne W. says:

    During Viet Nam, I worked at a mini shipyard in Quih Nhon. One of the boats we worked on had Detroits. The mechs overhauled 12V71 engines, one pair bolted together for each prop, about 4 FT dia. They had twin superchargers and turbochargers. I am not a diesel mech, but when they were done overhaul, they ran around 3900RPM, I think, during sea trials. They were great to hear run!!!

  40. Dan Mag says:

    I have 671 TIB in my boat with 3000 hours on them. I changed the fuel filters every 50 hours and the oil every 100 hours. I have had the boat 14 years and only replaced a starter in 14 years. The motors do leak some oil after 60 hours but not much. I run the engines at 19 -1950 rpm.(not 2150).

    How many hours will I get out of these motors??????????????

    TY

    Dan Mag

  41. BOB HOMER says:

    I worked at Redford for 22 years, leaving in 1988 when sold to Penske. As a Receiving Inspector there quality was important. Every outside purchased part not made in-house had many checks to go through before acceptance. I believe we made the highest quality engines and history and customer satisfaction proves it. The 2-stroke 53’s and 71’s have been proven in war and troops swear by them.

  42. ednaldo miguel ferreira junior says:

    hi eric, what´s up?

    my question is:

    i have a 671 engine in line model 1063-7005 (typical power generator unit) and this engine was tested at 134 hp at 1200 RPM ,so i´d like to turn this engine in 1063-7000 (typical industrial power take off unit )with 180 hp at 1800 rpm.

    Is it possible?

    Regards,

    Ednaldo

  43. Jessebob says:

    I’m working on a 1974 tug boat powered by two 12v71s with blowers. Throttle hung wide open causing it to run about 2700 rpm. Spitting out a few valve springs in the process. New engine has been sitting on an engine stand for 12 years and hadn’t even had oil run through it yet. It shuts off when taken out of gear and doesn’t hesitate to restart. What adjustments can I make to stop that from happening?

  44. Robert Wright says:

    Guys, I have a 1984 Post Marine 43 with 2 1988 Detroit 671T and they have Jabsco saltwater pumps on them. But been having trouble with them blowing water like crazy. Had the port rebuilt but still throwing water but not as bad as before, but bad enough to give me some concern. Can anyone tell me if there is different maker of pumps that will work for me and not cost me a arm and a leg.

  45. Mike Partain says:

    Are there any exterior differences between the 2-valve and 4-valve heads? My marine 6-71N’s are difficult to work around.
    Thanks

  46. Per Landin says:

    I have 2 v71 12 cyl in a boat hadn’t been running for many years one is fine but the other went up to 3500 rpm kept running when I pushed the stop.
    One service guy told me to dismount all injectors one or several is stuck in full throttle ?

    Any advise please

    Per
    Italy

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