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12V71TI fuel burn graph

Discussion in 'Engines' started by Anthony hall, May 2, 2021.

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  1. Anthony hall

    Anthony hall New Member

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    Does anyone have a fuel burn chart or graph for the DD 12V71 Ti series engines installed in a late 80"s
    Viking 63 Motor yacht? Anything would be helpful Thanks
  2. Capt Ralph

    Capt Ralph Senior Member

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    With TD of ZF clutch?
    The ZFs were used for the taller HP models.
    We have the stock DDC 650 shaft HP with TD clutches.
    PM me with your e-mail address and HP tune and I'll dive into my archives.

    Bert Fuel 001a.JPG
    Last edited: May 2, 2021
  3. Capt J

    Capt J Senior Member

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    I ran a 75' Hatteras with 12v71TI covingtons and I think they were 760 HP although cannot remember. We burned 12 gphs for the pair at 1000 rpms, 80gph for both at 1900.
  4. Edad

    Edad New Member

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  5. Edad

    Edad New Member

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    Hope well.. At the 12 at 80 gph what was your average mph for your 75 vessel ? Thanks,, edad
  6. Capt J

    Capt J Senior Member

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    It was a 1987 65' Hatteras MY extended to 75. Heavy on fuel 16.5-17 knots. Lighter (1/2 fuel) and in the right location 19 knots at 1900 rpms. Held 1700 gallons of fuel.
    cognac likes this.
  7. Capt Ralph

    Capt Ralph Senior Member

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    For the faint of heart, That is over 4.2 Gallons per mile.
    If your trying to find economy in a big boat traveling faster than idle; Go back to sleep,, only in our dreams. :)
    At 19 kts, were doing 3.5 gallons per mile, down hill, with the wind, with some imagination. :rolleyes:
    Robertoman likes this.
  8. Nevin Taylor

    Nevin Taylor New Member

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    I have 1990 12V 71TI with turbos recently rebuilt with only a couple of hundred hours on them. I run them about 1200-1250 rpm. Slow I know so every once and awhile push them to 1800 to clean out the air boxes. However the last couple of thousand miles running both engines with 30KW generator I have been getting about 1-gallon per mile. I know most would tell you this is impossible, but with a total weight of 100K my hull allows the boat to run really nice and at 2300rmp we can do almost 30 knots. I wouldn't believe it myself if I had not experienced it. I have found that if you keep the hull clean, props and drive shaft tru, and fresh oil these engines will treat you right.

    Great specification sheet I came across along with a good history on Wikipedia.
    https://www.dieselpartsdirect.com/documents/detroit-diesel-specs/12v71ti-marine.pdf
    https://en.wikipedia.org/wiki/Detroit_Diesel_Series_71
  9. Capt J

    Capt J Senior Member

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    Those engines burn about 80 GPH at 1900 rpms. At 1000 rpms they burn 12 gph for both, 1200 25 gph. You should really run them at high cruise for 30 minutes every 6 hours at most (1900 rpms+) for longevity. But would make more sense for you to run at 1000 rpms and then cruise for 30 minutes every 6 hours, for fuel burn and longevity.
    Robertoman likes this.
  10. Capt Ralph

    Capt Ralph Senior Member

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    2307A915-4458-4A6B-BCDC-4771BD01225C.jpg
  11. rtrafford

    rtrafford Senior Member

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    I'm running 12v71TI's now at around 750 HP each. I'm cruising at 1375, burning a combined 22 GPH at 10.5 knots with a generator running...
  12. Capt Ralph

    Capt Ralph Senior Member

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    At your hull / length / speed, That is better than us.
    Your probably just under 175HP per engine at that RPM.
    Ah the blessings of an ole long skinny boat.

    You using 7N95 injectors and dry turbos?
  13. rtrafford

    rtrafford Senior Member

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    Yes, and there's a part of me that would like to swap these out for modern sixes for weight and economy. I've got a bit of a tick about the buildup of carbon on the turbos and coolers. I just removed and cleaned them all this past summer. I've thought often about dropping down to 550 HP with a low reduction and big wheels for dockside torque...
  14. Capt Ralph

    Capt Ralph Senior Member

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    550HP natural will require new pistons.
    Just keep clean fuel it her and run her up from time to time.

    Carbon on the inter coolers??
  15. bernd1972

    bernd1972 Senior Member

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    What kind of vessel are you running rtrafford?I would appreciate to know your length, beam and tonnage.
    Curious as seeking some compareability as well. Did a fuel calculator for 12V-71TI engines, but feel I am still a little on the optimistic side so searching for the right correction factor to adapt it to realistic numbers. I am sill trying to figure out what speed to expect at any given RPM for 70ft, 55t.