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blow by - is this normal for a rebuilt mercruiser?-gctid826391

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    blow by - is this normal for a rebuilt mercruiser?-gctid826391

    I recently had a rebuilt merc 5.7(non vortec) installed in my boat...

    is this normal blow by for a rebuilt? this was between hours 65.7 and 76.4 on this engine...yesterdays fishing trip...see pic


    Attached files

    1997 Bayliner Trophy 2352
    5.7 Mercruiser/Alpha I Gen II /Full Closed Cooling
    San Diego, CA

    HookEmDanO out ......

    the more people I meet the more I love my dogs !

    #2
    a newly rebuilt engine will have more blow-by that what an engine with a few hundred hours on it will have. the rings arent seated yet and they are the single determining factor on how much blow-by an engine has...

    but also, under the valve covers where the blow-by vent is, there is a separator pod that must be intact and not damaged, as this is suppose to let most of the oil separate out of the steam and gasses that are venting. if this pod is damaged it cant do its job properly and so the gasses will carry more oil out of the engine.

    I wouldnt even begin worry about the blow-by until after 35-50 hours, but even then if it seems like more than normal, it could clean up as the engine breaks in more... but after 150 hours if its still has a lot, there is a ring problem.


    NU LIBERTE'
    Salem, OR

    1989 Bayliner 2556 Convertible
    5.7 OMC Cobra - 15.5x11 prop
    N2K equipped throughout..
    2014 Ram 3500 crew cab, 6.7 Cummins
    2007 M-3705 SLC weekend warrior, 5th wheel
    '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
    Heavy Equipment Repair and Specialty Welding

    Comment


      #3
      "Centerline2" post=826393 wrote:
      I wouldnt even begin worry about the blow-by until after 35-50 hours,
      I stated in my post that this was hours 65.7 to 76.4....so well past the 35-50 hours
      1997 Bayliner Trophy 2352
      5.7 Mercruiser/Alpha I Gen II /Full Closed Cooling
      San Diego, CA

      HookEmDanO out ......

      the more people I meet the more I love my dogs !

      Comment


        #4
        "hookemdano" post=826396 wrote:
        "Centerline2" post=826393 wrote:
        I wouldnt even begin worry about the blow-by until after 35-50 hours,
        I stated in my post that this was hours 65.7 to 76.4....so well past the 35-50 hours
        yep, seen it but forgot.

        if you could get a filter of some type on the tubes, you could tell if if one side is producing more oil that the other side...

        when running on the muffs (or in the water), at a fast idle of 2500rpm, holding you finger over one of the vent tubes, is there a lot of pressure or "exhaust" from the other tube?

        is the crankcase overfull by any chance?

        its possible that just the way the oil is being splashed around by the rockers that an abnormal amount of it is getting into the separator box.... this is not common but not unheard of either.

        I would look at all possibilities, as its rare that anyone who has the smarts to put an engine back together would install the wrong rings or incorrectly... but again, its not unheard of..


        NU LIBERTE'
        Salem, OR

        1989 Bayliner 2556 Convertible
        5.7 OMC Cobra - 15.5x11 prop
        N2K equipped throughout..
        2014 Ram 3500 crew cab, 6.7 Cummins
        2007 M-3705 SLC weekend warrior, 5th wheel
        '04 Polaris Sportsman 700 -- '05 Polaris Sportsman 500 HO
        Heavy Equipment Repair and Specialty Welding

        Comment


          #5
          UPDATE

          I took the boat into the shop today...my mechanic said that this should not have happened...he is going to perform a leak down test and do a compression test....more info later
          1997 Bayliner Trophy 2352
          5.7 Mercruiser/Alpha I Gen II /Full Closed Cooling
          San Diego, CA

          HookEmDanO out ......

          the more people I meet the more I love my dogs !

          Comment

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