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Man Diesel?

Discussion in 'Post Yacht' started by jerry bredow, Apr 9, 2016.

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  1. jerry bredow, Apr 9, 2016
    #1
    jerry bredow

    jerry bredow Member

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    I have a 1998 Post 47 foot with the Man Diesels 2848 model. I run the boat at about 1800 rpms and it runs great, but I have a question about running at lower rpms. I am looking to take the boat into the Chesapeake this season for a few weeks to explore. Will running the boat at a trawler like speed be bad for the motors since the turbos will no be at speed?
  2. baltimore bob, Apr 9, 2016
    #2
    baltimore bob

    baltimore bob Member

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    Like any high performance diesel, just run them up occasionally to clear them out. Let me know when you do the trip....we should hook up!
  3. Capt J, Apr 9, 2016
    #3
    Capt J

    Capt J Senior Member

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    +1. About every 6 hours just bring them up to 1950's for 30 minutes. I've also found the MAN's like to run harder and 1950-2000 rpms or close to 80% load they seem to run cleaner, smoother, and quieter than 1800 rpms. One boat I run with 1100hp Common rails 2100-2150 rpms is 80% load, they top out at around 2360 rpms.......running it at 1800 and they just sound like they're lugging and run dirtier.
  4. olderboater, Apr 9, 2016
    #4
    olderboater

    olderboater Senior Member

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    We have three boats with MAN's. 800 hp's, 1200's, 1360's. 80% on those three in that order are 2000 RPM, 2100 RPM, and 2000 RPM. In all three cases that is 300 RPM off of maximum.
  5. Capt Ralph, Apr 9, 2016
    #5
    Capt Ralph

    Capt Ralph Senior Member

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    Funny this came up;
    I'm delivering my last MAN boat south and away (Yea). New owner and previous owner have been talking.
    V8-900CRMs and my instructions are to cruse at 70% load max.
    That still pulls 16/17kts and I'll be bingo fuel before the sun goes down whatever speed I do.
    Oh well, no fun for us Crappers.

    BTW, after this I will have a new MAN $$ rate; Bozillon per hour,, that's just under the MTU godzillon per hour rate.
  6. olderboater, Apr 9, 2016
    #6
    olderboater

    olderboater Senior Member

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    What size boat that only gets 16-17 kts at cruise out of those engines? Our slowest boat with MAN's runs 26 knots at 70%
  7. Capt Ralph, Apr 9, 2016
    #7
    Capt Ralph

    Capt Ralph Senior Member

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    SeaRay SD58.
  8. olderboater, Apr 9, 2016
    #8
    olderboater

    olderboater Senior Member

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    Well, they're only 861 hp each, but that boat still is supposed to go 30 at WOT and cruise at 26 knots. The one you're delivering has some issues.

    Didn't Mercruiser do some things to those MAN's as well?
  9. Capt J, Apr 9, 2016
    #9
    Capt J

    Capt J Senior Member

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    They like to be run at 80% load and haven't seen any issues running them that way....I delivered a few of those boats long distance....Ft. Laud to Conneticut, another one from Delaware to Toledo, OH. 80% load and it cruises at 25.5-26 knots.....70% load and 16-17 knots seems like a bad speed as it's at maximum plow.
  10. Capt Ralph, Apr 10, 2016
    #10
    Capt Ralph

    Capt Ralph Senior Member

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    Yea, Yea, I've Never typed with you kids ever before about running a boat and we know all of these things.
    But I have this green thing problem, I like to have some in my pocket. This involves trustfully following instructions by the person who has those green things to spend.

    Again, I'm out of fuel before the sun splashes anyway.

    On a plus side, that max weight AB rib is off the back porch. That's over 1000 pounds weight loss in the asp.
    That should help the bow come down (way down) and pick up some serious speed at 70%.
  11. jerry bredow, Apr 10, 2016
    #11
    jerry bredow

    jerry bredow Member

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    Baltimore Bob, I assume by your screen name that you are close to baltimore. Would you have any insight into an area that we can anchor for the evening. Always wanted to spend a night or two on the hook. Not sure yet if we will be entering the bay from Virginia or the C&D. Always seeking opinions on nice places to stop over.
  12. Beau, Apr 10, 2016
    #12
    Beau

    Beau Senior Member

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    Jerry
    I have a 50 with 820's, we have slow motored all over the east end without problems. In fact, depending on your gears and shaft seal set up, you can shut one down, and alternate from side to side ...
  13. baltimore bob, Apr 10, 2016
    #13
    baltimore bob

    baltimore bob Member

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    When you decide if you are coming in the top or bottom I'm sure I can point you to a decent spot!
  14. jerry bredow, Apr 12, 2016
    #14
    jerry bredow

    jerry bredow Member

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    At this point I think that I will be coming in from the C&D. I believe this will allow me to be less depended on weather conditions in the ocean. I have a 28 mile run to Cape May, after that a little run in the delaware bay. By the time I get to the C&D water conditions would be less of a concern.