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Oil Coming out of Breather and Oil Cap

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  • Oil Coming out of Breather and Oil Cap

    I have a 2004 Larson SEI with a Mercruiser 3.0 in it. I have had the engine rebuilt once already and shortly after the rebuild I noticed that the pressure coming out of the breather to the spark arrester, and the oil cap will pop off sometimes. Oil comes out and builds up in the bilge. I did a compression test on it and all of the cylinders are in the range of 130 to 140. The air coming out is not smoky and the oil is not milky at all. I am ruling out the head gasket as I have OK compression and I dont think it's rings for the same reason as it got new rings with the rebuild.

    Any help would be great. I am fairly experienced and can do most diagnostic tests but am slightly stumped by this one.

    Thanks
    Brandon

  • #2
    Time for a leak down test. You pressurize the cylinder through the spark plug hole and then locate where the air is escaping by listening. Either it goes out the oil filler, meaning rings, the carb, meaning intake valves, or the exhaust, meaning exhaust valves.

    17 Foot '90 Bluewater
    Alpha 1 3.0 Merc - repowered in 2016
    now - 4.3L Vortec - Alpha 1 GenII
    Honda BF100L kicker
    Engine custom - Transom 0D65328 - Drive 0D648864
    If you ain't fishin, then yer working too much.

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    • #3
      I have had the engine rebuilt once already and shortly after the rebuild I noticed that the pressure coming out of the breather to the spark arrester, and the oil cap will pop off sometimes.
      Sorry to hear, but who ever did your rebuild didn't do it right
      Blow by comes from rings not seating.

      Hope it wasn't someone tried to dupe you and not bore the block and just put a set of rings on it
      94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
      95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
      07 Seadoo GTX
      Merc Adults Only VP Adults Only
      G-Dad always said "First Liar doesn't stand a chance"

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      • #4
        Even with the compression numbers I am seeing?

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        • #5
          130 is a tired engine. You should be 150s at the very least on a fresh rebuild. See what happens with a wet compression test.

          '86 Glastron Conroy X-19, Merc 170
          '04 Carolina Skiff J14, 25 hp Mercury
          Richmond/Montross, VA

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          • #6
            Motor is out already. Best place to purchase a reman? Michigan Motorz?

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            • #7
              Leak down test pretty much showed its gotta be the rings.Motor is out already. Best place to purchase a reman? Michigan Motorz?

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              • #8
                MM has had no complaints here that they didn't take care in short order.
                94 Formula 27PC Custom 509MPI MEFI3 , B3 XR
                95 Rinker 232 w/ 7.4L Carb 0F425011 B1 0F486471
                07 Seadoo GTX
                Merc Adults Only VP Adults Only
                G-Dad always said "First Liar doesn't stand a chance"

                Comment


                • #9
                  Sign up today
                  Just placed an order with them. Knowledgeable, extremely friendly so far.

                  '86 Glastron Conroy X-19, Merc 170
                  '04 Carolina Skiff J14, 25 hp Mercury
                  Richmond/Montross, VA

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