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Detroit 8v71 recommended rpm

Discussion in 'Engines' started by wayneCCC, Jul 28, 2015.

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  1. wayneCCC

    wayneCCC New Member

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    May 13, 2015
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    Location:
    Vancouver, BC
    Ah, just miss it by a couple years. Thank you all very much for the information, it certainly helps with my understanding of the engines and what should be a target speed for economy, longevity etc. I will be doing some experimenting this weekend and will post what I come up with.
  2. wayneCCC

    wayneCCC New Member

    Joined:
    May 13, 2015
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    15
    Location:
    Vancouver, BC
    Well I did some rpm to speed tests earlier this week.
    1200 rpm. 8.8 knots
    1400 rpm. 10 knots
    1700 rpm. 12 knots
    1800 rpm. 13 knots
    2300 rpm. 18 knots

    It was starting to get up on plane but didn't want to run for too long above 1800. Also didn't know if trim tabs worked or not but now I have confirmed they do. I have it on the hard to get bottom and hull paint done.
    Bottom and props were all clean and in great shape. Will be back in the water next week and will test the speeds again.
  3. Capt J

    Capt J Senior Member

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    Jul 11, 2005
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    Why do you not want to run for too long above 1800??? Your engines were designed to run 1900 rpms at cruise all day long and it's good for them and keeps the airboxes clean. On your type of boat, using the trim tabs will generally get you a lot better cruise speed and fuel economy.
  4. wayneCCC

    wayneCCC New Member

    Joined:
    May 13, 2015
    Messages:
    15
    Location:
    Vancouver, BC
    I don't know, other then the original owner said that is how he ran it. I am knew to Detroit diesels, and learning all the time. Thank you for the information.