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MAN V1550s best RPM range to run for a long healthy life

Discussion in 'Viking Yacht' started by MSviking, Aug 7, 2012.

  1. MSviking, Aug 7, 2012
    #1
    MSviking

    MSviking New Member

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    Nov 29, 2011
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    OB Alabama
    I have a Viking 54C with MAN 1550s with right at 1000 hrs and the engines have been flawless and fast! I usually spend 90% of my time trolling with 10% running in or out, normal cruise is around 80-85% load on engines, running 32-34 knots. I assume this is a comfortable "zone" to run the boat in? Just wondering and trying to learn the best way to maintain and use my engines.

    Robert
  2. C4ENG, Aug 7, 2012
    #2
    C4ENG

    C4ENG Senior Member

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    I asked the engineers of CAT and MTU why they suggest running at high load (80% or so) and they explained to me it is because of the design of the cylinders and piston rings. They are engineered to fit together tightest at high load with the amount of heat being produce in the cylinders. When every thing fits at tightest potential, then there is minimal blow by. Blow by puts fuel in your oil. When at low load, that is when you are having the most blow by introducing the unburned fuel in the oil which causes other issues.
    There was just an interesting topic in Tech Discussions about fuel and oil issues from blow by at low load with many interesting opinions, views, and experiences to choose from.
  3. Capt J, Aug 7, 2012
    #3
    Capt J

    Capt J Senior Member

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    I'd run them at 80% as recommended by the manufacturer. One thing I've seen that wears on MANS since they don't have as much torque as CATS are on slower and much heavier boats where they gain and lose rpm's going up and down waves (load factor changes) and sometimes it's better to run them a little harder if the hull maintains a constant speed. That is not the case on your 32 knot sportfish.

    I agree, the engines like to see a constant temperature with all of the parts/components and expansion and contracting in the parts creates wear.......
  4. MSviking, Aug 7, 2012
    #4
    MSviking

    MSviking New Member

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    Sincere thanks for both responses. I did a search and read other posts in the Tech section on the same/similar issues.

    I take it, what you are both saying is find a "happy" spot close to 80% load independent of what RPMs that might be (I just don't have the data yet). As to the torque and change relative to seas, I have heard this, but have yet to experience it, may be that I am more of a fair weather fisherman and have not run much in large seas.

    Thanks again.
    Robert