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Oil Analysis on MAN 2840's

Discussion in 'Technical Discussion' started by jhartog, Aug 7, 2009.

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  1. jhartog, Aug 7, 2009
    #1
    jhartog

    jhartog New Member

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    Hello
    I have been lurking for awhile now and have thoroughly enjoyed [most] of what I have read. Certainly, there is no end to the expertise available here.

    I am looking at a 1996 boat with 820 hp MAN 2840LE401's, with just shy of 2200 hrs. At sea trial, the engines started right up, with no white/gray/black exhaust.

    Engines are rated for 2350 top RPM''s but we only achieved 2230/2240 p&s respectively. Turbo boost on stbd was also low. btw - original wheels (I am informed) were 39 x 39 but the wheels on this boat are 39 x 41.

    I did not have a compression test performed (yet).

    Oil analysis came back (analyzed by CAT) and engine surveyor said most readings 'OK' but suggested new piston rings and liners.

    I sent the survey and analysis to another MAN diesel surveyor for a second opinion who suggested much more maintenance should be performed but even more interesting said that MAN does not have a spec for oil analysis.

    My question - is there such a thing as a 'spec' for an oil analysis since all oil should show some degree of wear & tear. Of course, having an analysis provides a baseline going forward for future comps.

    I cannot obtain concrete info from the seller re past engine maintenance so I will assume it is minimal. Given that the engines ran well and no exhaust issues at start up - I'd like your thoughts.

    TIA
  2. AMG, Aug 7, 2009
    #2
    AMG

    AMG YF Moderator

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    Hi, if you had a start from cold engines with no smoke, it is an exception.

    If they were warmed up recently, it would be normal.
  3. NelsonP, Aug 7, 2009
    #3
    NelsonP

    NelsonP New Member

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    Before I would go for an extensive maintenance work, I would check the revs at WOT at neutral. If you do get 2350 rpm then as a second step I would examine the cutlass bearings in the shafts. Are you certain that these were replaced when due. Normally they last for up to 3 to 4 seasons.

    I had the same problem once, with DE2842LE406's and as soon as I had them replaced all rated rpm came back again. And a little more
  4. jhartog, Aug 7, 2009
    #4
    jhartog

    jhartog New Member

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    Hi
    Boat had been brought in the day before for the survey - down time after runnning about 15 hours before we started them up - still slightly warm.
  5. jhartog, Aug 7, 2009
    #5
    jhartog

    jhartog New Member

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    Thank you. As I have not been able to obtain detailed maintenence info, I do not know what has or has not been serviced. I will put your suggestion on my list of items to investigate.
  6. Loren Schweizer, Aug 7, 2009
    #6
    Loren Schweizer

    Loren Schweizer YF Associate Writer

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    Welcome to YF, BTW.
    I would have MAN do a compression test along with the standard borescope look-see.
    That Cat oil analysis likely found a lot of iron in the sample, but, with the low hours, that could have been due to all the rust being scraped off subsequent to a start-up after an extended period of non use: 2200 hrs. in thirteen years is a pretty low number.

    MANs are noted for their better-than-average longevity and I'd be surprised if these required rings & liners.

    Good luck.
  7. Capt J, Aug 7, 2009
    #7
    Capt J

    Capt J Senior Member

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    Unless there was something bad that happened to the MAN's such as the vessel sitting for a year without being run at all, you should not need pistons/rings and liners. Why does the surveyor recommend that? I am running a boat with the same MAN's that has 3800 hours on them and they went through survey fine. The MAN dealer said they should go 5-6000 hours before rebuilds if maintained. It is very common to lose a 100 rpm's on an older boat, you may gain that back just by doing a fresh bottom job, having the props reconditioned, prop speed, and new cutlass bearings.

    If you're not getting any smoke at cruise speeds and WOT, I would say 2200 hours is nothing to worry about. A compression test will tell you where the engines stand, but you might as well get the injectors checked while they're out and the labor has been paid for, but you don't own the boat yet. It's part of the 1000 hours service to check injectors, adjust valves, and clean all seawater coolers, raw water impellors, oil and filter changes and fuel filter changes. The dealer quoted $17k for the pair to do the 1,000 hour service here in South Florida (DSOA).

    What were the numbers on the iron, copper, and tin? I agree most of the time (especially when you don't know the history) iron is from sitting and some rust that's been scraped off and something to monitor but not worry about.
  8. jhartog, Aug 7, 2009
    #8
    jhartog

    jhartog New Member

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    Thanks Capt.
    The #'s for Stbd - Cu: 23 Fe: 102 Sn: 0
    The #'s for Port - Cu: 30 Fe: 85 Sn: 0

    Of course, the boat was hauled during survey and the bottom was quite clean - just needs a new coat of anti-fouling.

    I have to say the engines started right up, very clean, and the boat ran well during sea trial - I just want to make sure I go through all the proper steps before committing.

    I have decided to go ahead with the compression test and see how that comes out. Certainly worth the $2K. Also to have the props reset to 39 x 39 from 39 x 41. That should be good for at least 100 RPM's

    Thanks to everyone for their input.
  9. Capt J, Aug 7, 2009
    #9
    Capt J

    Capt J Senior Member

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    Each 1" of pitch you take out on a diesel boat usually gives you an additional 50 rpms. The numbers are a little high, but not astronomically..... 100 parts per million. It sounds like it has been some time since the oil was changed in the engines and that could cause those numbers. I'm willing to bet compression would be good......but if you do a compression test and it's all good......buy it, do an oil change, run it 50 hours and change it again and you should be good......
  10. K1W1, Aug 8, 2009
    #10
    K1W1

    K1W1 Senior Member

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    Hi,

    Lorens suggestion for a borescope is a good one, while a recent start up after a long period of non running can get you going, it is the damage done by the rust that will rear it's ugly head sooner rather than later.

    Ask the guy doing the borescope to particularly look at the full length of the liner and to examine the Valve seats, if these all look good the engines should be good for the most part for a lot more hours yet.
  11. jhartog, Aug 8, 2009
    #11
    jhartog

    jhartog New Member

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    thanks to all for your invaluable input. Jack