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MAN D2842 LE406, 1200 HP

Discussion in 'Engines' started by Lazy Days, Dec 2, 2025.

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  1. Lazy Days, Dec 2, 2025
    #1
    Lazy Days

    Lazy Days New Member

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    Dec 2, 2025
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    Tananger, Norway
    I understand for earlier threads that the MAN 1200hp LE406, 1200 HP is the very last development of their fully mechanical engines, produced for decades and widely regarded as very reliable.

    From earlier threads I also read that the engine needs a rebuilt at some point (running hours), depending on usage. What would be the typiscope of such a rebuild?

    My engines now have close to 3 000 hours on them (sits in a Princess/Viking 20M from 1999), most of these at low loads.
  2. bernd1972, Dec 17, 2025 at 8:19 PM
    #2
    bernd1972

    bernd1972 Senior Member

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    Flensburg, Germany
    Treat them well, keep them happy with clean good oil, do the standard maintenance by the book, keep the cooling system clean and run them. Do not worry too much for the next 5.000-10.000hrs.Monitor oil and coolant condition and amount. If anything changes noticeably figure out what´s up.
    Capt Ralph, SplashFl and butch w like this.
  3. Mambo42, Dec 19, 2025 at 8:48 AM
    #3
    Mambo42

    Mambo42 New Member

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    Croatia
    I was looking at a boat with the identical engines, called MAN and asked the same question: 'how long before overhaul'.
    MAN told me to have the engine checked thoroughly, which means oil samples, boroscope, compression test, check the turbo, pressure test the oil cooler, check / clean the intercooler (if it has one), check all the connections and after that service the engine properly.

    They told me that if you service the engine on a regular basis these engines can last up to 50.000 hrs. However, that is commercial use, where the engine runs basically all the time.
    If the engine has been maintained well the engine will last for many hours more.
  4. Capt Ralph, Dec 19, 2025 at 10:27 AM
    #4
    Capt Ralph

    Capt Ralph Senior Member

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    Low loads really does not mean better (IMO).
    When your tuned to make 1200HP, efficiencies at 400HP are not the best at that load (40% or less?).
    Yes, you may be making better MPG but a fully mechanical engine may not be combusting the fuel completely at low loads.
    Usually not good for pistons, rings & liners.

    This is why oil labs and bore scope inspections are so important.
    These help predict time to overhaul before a major failure (new engine) happens.

    Commercial rated engines are matched and tuned to a operating load and run there it's whole life.
    You need 463 HP, tune there (only there) and see many thousands of hours.
    Yes, these life spans are impressive but the recreational engine can sadly never compare.
  5. motoryachtlover, Dec 19, 2025 at 1:51 PM
    #5
    motoryachtlover

    motoryachtlover Senior Member

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    In a recreational marine application I think cylinder wall rust from sitting with valves open and salt air getting into the engine will greatly reduce the hours you will get out of the engine. I think you will be very lucky to get 5000 hours out of recreational marine engine. A genset on land running almost 24/7 sure 20,000 hours
    Capt Ralph likes this.