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Nordhavn 76 Repower

Discussion in 'Nordhavn Yacht' started by lovinlifenc, Sep 14, 2010.

  1. lovinlifenc

    lovinlifenc Member

    Joined:
    Mar 28, 2010
    Messages:
    135
    Location:
    Wilmington NC
    First, I must say that I plan on buying a 62 or larger Nordhavn sometime in the next 5 years. I would like to make sure that I understand why this is occurring so I can avoid a similar situation.

    I have heard that there is a new Nordhavn 76 in the PNW that is already going through a re-power from MTU to John Deere.

    Supposedly, the MTU was mis-sized for the boat and the dry stack was spewing lots of soot when running the MTU at 50%, which is all that the hull required. The owner got sick of cleaning the soot on his decks and canvas duiring the first few weeks or months of ownership, so he is now pulling the MTU and installing a JD. There is also speculation that the MTU software is not set up for a dry stack installation. I wish I had the model numbers of the motors, but I do not.

    Is excessive soot a common problem when running a diesel motor at less than 70 or 80% load with a dry stack setup? Does anyone have specific knowledge of this situation that can help me understand it? How much would a re-power of this magnitude cost?
  2. Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,432
    Location:
    Fort Lauderdale
    I do not know how running a dry stack would effect the computer controls of a MTU.

    What I do know. I know that the fuel curves on the DDEC/mtu system can be adjusted and changed depending on what you're looking for. I worked on one boat with 16v2000's where the curve was richened up to provide more low end torque.

    I have run several of the different MTU's (series60, 10v2000, and 16v2000) at 50% load or less for extended periods of time (like 12-36 hours) with no soot issues, and not even a disclored transom.

    A john deer's or a Luggers or even the Cummins KTM11 life span and design might be more suited to the usage of a Nordhaven over an MTU. It is quite possible that the owner used the MTU until it accrued the amount of hours necessary for a rebuild and decided to re-power instead. It is much better for the engine to be matched to the cruising speed of the boat (displacement) where it sees 80% load. Running 50% load all of the time may shorten the lifespan depending on how well the computer can adjust the fuel curve and whatnot
  3. K1W1

    K1W1 Senior Member

    Joined:
    Sep 30, 2005
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    Hi,

    The use of Dry Stack on your main engines is actually a better choice than a wet one from the engines viewpoint.

    Soot coming out is the biggest drawback, this can be caused by a lot of things.

    Poor Quality and or Dirty Fuel, Fuel Filters, Air Filters and incorrect maintenance can all be sources of gunge forming in the pipes.

    Light load running doesn't help with this at all.

    Steel Pipes can also rust and then big chunks of soot covered rust will be thrown out.

    Burning a Lube Oil with a high sulphated ash content can also add materials to the inside of your pipes which will come off from time to time and make a mess. This type of Lube Oil is also death to soot filters etc.

    A good particle filter/soot burner system is a great asset and is now standard fitment on a number of large MTU Powered yachts where they are used at lower power settings to keep the dry stack discharge clean.