Detroit Diesel 71 series - inline vs. Vee

Discussion in 'Inboards' started by goodwilltoall, Jul 3, 2016.

  1. goodwilltoall
    Joined: Jul 2010
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    Location: nation of Ohio

    goodwilltoall Senior Member

    Greetings,
    Found an older uniflite with a 6v71 which is new to me (thought they were all inlines). So far am considering using good parts for new build but was wondering what the reliability and parts availability is for these? Prolly would just sell the engine but how difficult would it be to change to dry stack? Currently its a maze of pipes n valves all over the place.
     
  2. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    It is a very common engine. You can get parts without problem.
     
  3. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    To change to a dry stack is more a matter of running the exhaust pipe up thru the vessel.

    Some folks use lagging to lower the chance of touching the stack, neatest is fireplace double wall SS with the true exhaust pipe inside.

    A truck muffler will do fine for quiet , but the best of all is a generator "Hospital Critical" unit. They are heavy and expensive , but WORTH IT!!

    With a dry stack, you might as well install keel cooling too.

    With a hatch over the engine space an engine change is a weekend.

    And you will never need to winterize again.
     
  4. goodwilltoall
    Joined: Jul 2010
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    goodwilltoall Senior Member

    FF. That's the basic idea. Totally agree with using hospital muffler considering the reputation jimmy's have. Was lookn at manifold and last I remember it had pipes going into it from radiator as well as cooling water added at exhaust pipes right after. So trying to figure how to add keel cooling. Btw are vee and inline comparable with longevity?
     
  5. FAST FRED
    Joined: Oct 2002
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    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    The water cooled exhaust manifold would be hooked up to the engine coolant.

    The keel cooler will be a bit larger to accomodate the extra heat load.

    On our DD 6-71 the keel cooler is simply 2 lengths ( 20 ft each) of 1 1/2 water pipe with 2 elbows and a close nipple .

    Works fine in FL summer waters.

    One danger of a KK setup is over cooling, the return coolant could be very cool , most engines use a 20deg drop coming back from a radiator.

    A bypass thermostat in the lines to & from the KK solve the hassle .
     
  6. Capt Drake
    Joined: May 2015
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    Location: Florida

    Capt Drake Junior Member

    For the most part DD engines are all good and as mentioned before parts are easily available. As for the engine; even though its an old engine and newer electronic engines are available selling it, Its a sought out engine and moving it should be no problem. They are reliable engines and plenty out there; i have seen them still running with major damage while returning a boat to port, other than catastrophic failure the engine keeps on going.

    As for the exhaust and relocating the stack; one thing you want to maintain or upgrade if you don't have it is a water cooled exhaust and turbo, there was a time in the past some manufacturers didn't use them and becoming a known fire hazard.
    Relocating the stack is a matter of space and creativity, the hospital muffler is a great idea if you have the space since its bulky.
     
  7. goodwilltoall
    Joined: Jul 2010
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    Location: nation of Ohio

    goodwilltoall Senior Member

    Ok thanks,
    Its all very interesting but at this time there is more value using parts (hydraulic steering, rudder, doors, etc) rather than trying to save the uniflite. The engine was supposedly rebuilt and ran before it was put away so would most likely sell it, besides the 6-71's always seemed to big for my purposes (really like the 2-71, 3-71, and 4-71's max.
     
  8. WestVanHan
    Joined: Aug 2009
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    Location: Vancouver

    WestVanHan Not a Senior Member

    Check eBay for a ballpark price on rebuild kits for DD. Cheap.
     
  9. jehardiman
    Joined: Aug 2004
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    Location: Port Orchard, Washington, USA

    jehardiman Senior Member

    Big reason for V over inline in total height. Other than that...not much to choose between.
     

  10. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    The v6 dd are good engines but different than i6 even though they share many parts. V6 used a lot in buses, many converted to marine because of being a cheap swap. Some engines not converted 100% . I6 older engines typically, more balanced sand heavier built even if they are simpler. I6 pleasure to work on. At the end both excellent engines.
     
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