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MTU 16V 2000 M91

Discussion in 'Engines' started by Tadman, May 29, 2023.

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  1. Tadman, May 29, 2023
    #1
    Tadman

    Tadman New Member

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    San Pedro, CA
    I have a pair of MTU 16v 2000 M91 engines with 1900 hours. Can these engines be used at low RPMs for long periods? Can you run them for several days at around 800 RPMs, or do you need to heat them occasionally? Is there potential harm to these motors if idled for hours, the boat runs at 7.5 knots under idle. Thanks
  2. Capt Ralph, May 29, 2023
    #2
    Capt Ralph

    Capt Ralph Senior Member

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    What does your MTU dealer and/or MTU technical services say?
    Protect your investment with factory specs and please let us know what you find out.

    IMO; That is a heck of an investment, into that much HP and then do what the engines were not intended to do.

    Even our old Detroits get cool after a slow ride in hot ocean water. Pick up the rpm every once in a while to get some temps up for a few minutes and blow out the air boxes.
    I fear your left coast waters are cooler and your engines may never get warmed up till some real HP is produced.
    But here, I'm guessing.
    Contact MTU..
    Good luck.
    Last edited: May 29, 2023
    rtrafford likes this.
  3. YachtForums, May 29, 2023
    #3
    YachtForums

    YachtForums Administrator

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    Tadman’s avatar looks like a Bertram 70’ Skylounge. It’s been a few years since Bert built that boat so it’s doubtful he’s working with a dealer.
  4. Capt Ralph, May 29, 2023
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    Maybe need to start?
    I'm not going to tell him it is O K.

    IMO; @125+ HP per lung, the size of those pistons (oil cooled?) must be impressive and miles of oil galleries.
    The last thing wanted is a cold engine with cold oil and cold cylinder temps grinding away at idle.
  5. Capt Ralph, May 29, 2023
    #5
    Capt Ralph

    Capt Ralph Senior Member

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    I remember MAN trying a thermostat pack to help get some engine areas up to temp at slow RPMs.
    Maybe MTU has this (option?) and needs to be checked out.
  6. Pascal, May 29, 2023
    #6
    Pascal

    Pascal Senior Member

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    I ve been running a 110 MY with M91s. 4000 hours and both rebuilt in the last 2 years.

    Coolant is much cooler than cats, DDs or Cummins at about 160, 165 max. I asked the MTU mechanic who rebuilt them about running at 1000 rpm for long trips he said it was fine. I still run them up for the last half hour.

    idle or near idle may be too cool. I’d talk to a good MTU guy. Why not run on one engine at a slightly higher RPM and alternate every 30-60’?
  7. Tadman, May 29, 2023
    #7
    Tadman

    Tadman New Member

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    She is a 67E 2005. I have had her for three years with no engine issues so far change the oil every 100 hours. I spend a lot of time trolling and plan to run to Mexico but might as well troll along the way and save fuel at the same time. When on the water, I am not in a hurry, I like to enjoy every minute spent away from it all.
  8. AGP22, May 31, 2023
    #8
    AGP22

    AGP22 Member

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    I run the same engines. I've been told by the MTU guys who service them that you can run for a few hours either idle, or low rpm on a single turbo. But you must allow higher rpms for 10 minutes with the 2nd turbo on every so many hours to "clean up" the systems. I know idle operation saves a lot of fuel, but if you get waves across the beam, the boat must rock like crazy.