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Problem with Mercruiser 3.0 After Rebuild

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  • Problem with Mercruiser 3.0 After Rebuild

    Hi all, was hoping those out there with some experience with the Mercruiser 3.0 can provide some insight, not sure if I’m getting some bad gouge from the local machine shop or there is something there.
    Some background information, have a 2006 Sea ray 185 with a Mercruiser 3.0 that was I bad shape, had hydro locked, lots of corrosion, bad head gasket etc. I took it to a local machine shop and he tore into it while I was on travel and replaced everything to include stainless without checking with me. If I knew it was that bad, I would just have replaced the engine I believe. Regardless, took it out for the first time and took it easy, ran okay for the first 40 minutes or so, thought the power was a little lacking, then the oil pressure fell to zero and I heard some knocking. I shut it down immediately and let it sit for a while. I was out in the bay so I thought I would see if it would start so I could limp to the ramp. It was sluggish/dragging starting, but started and pressure was back up, however there was a discernable knocking sound if I increased the RPM’s. I limped it back to the ramp and last weekend pulled the engine (again!)
    I took it back to the machine shop and he insisted that he didn’t understand what it could be. He called me today and claimed the square gasket had blown out and that there was water in cylinder number 2 and the head gasket was fine. He provided that the outdrive had gotten clogged and caused the water to get in the cylinder because he could see a burnt spot on the exhaust manifold. Does as a note the manifold/riser, water pump and outdrive impeller are all-new, first time on the water.
    I have a bit of experience with engines albeit autos and this simply doesn’t track with me. The frustration is regardless what he does I don’t feel comfortable taking this engine out again. Like to hear your opinions/experiences and thanks in advance.

  • #2
    Don't see how an outdrive getting clogged, and even if it did it would not put water in a cylinder.

    My guess is the crank was not turned or measured correctly and it spun a bearing (the knock and low il pressure)
    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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    • #3
      Seems like engine re-building is not in this mechanic's wheelhouse. 'Creative' explanation though
      Best regards, Ted . . . . Cape Cod, MA

      Current Boats: Formula 330 Sun Sport, O'Day Mariner Sail #3224, Sunfish
      Past Boats: Catalina 22 Sail #10531, Formula 242 Sun Sport
      Twin Mercruiser 7.4 LX MPI (0F802036, 039), Bravo 3's (0F806198, 199), Mercury 7.5 HP (1969), Johnson 4.5 HP (1980)

      My Boating Web Pages: http://www.tpenfield.com

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      • #4
        Thanks, not sure if I’m off base but the only way water can get in the cylinder is through a head gasket or crack in the block?

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        • #5
          Originally posted by AMMO DAWG View Post
          Thanks, not sure if I’m off base but the only way water can get in the cylinder is through a head gasket or crack in the block?
          Exhaust manifold ,elbow, or gasket between them or crack in head

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          • #6
            Originally posted by Scott06 View Post

            Exhaust manifold ,elbow, or gasket between them or crack in head
            What Scott said.
            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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            • #7
              Thanks, not sure if I’m off base but the only way water can get in the cylinder is through a head gasket or crack in the block?

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              • #8
                Sorry for all the questions, just want to be prepared when I deal with this guy, how does the elbow or blown gasket contribute to water in a cylinder. Would it only be in number 2 or all cylinders? Thanks again for all the help

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                • #9
                  Originally posted by AMMO DAWG View Post
                  Thanks, not sure if I’m off base but the only way water can get in the cylinder is through a head gasket or crack in the block?
                  No - as stated, any leak in the manifolds will put water in the cylinders - that includes intake and especially exhaust manifolds. Most common way is cracked exhaust manifold or corroded out passageways at the manifold riser connection. Risers are exactly the same capable of leaking and putting water into your cylinders.
                  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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                  • #10
                    Thanks, the exhaust manifold, riser and exhaust hose were all brand new, guess it's possible they were defective

                    BTW I see you repowered to a 4.3, are you happy with that upgrade, I have most of the parts to include the outdrive to do the same, might just get this engine fixed and do the same.
                    Last edited by AMMO DAWG; July 2nd, 2020, 06:55 PM.

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                    • #11
                      Prior to bolting the riser

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                      • #12
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                        Originally posted by AMMO DAWG View Post
                        Thanks, the exhaust manifold, riser and exhaust hose were all brand new, guess it's possible they were defective

                        BTW I see you repowered to a 4.3, are you happy with that upgrade, I have most of the parts to include the outdrive to do the same, might just get this engine fixed and do the same.
                        I can see why this is a confused diagnosis. Not sure how to help. You can test a manifold with it removed by filling the water jacket with acetone. Acetone will quickly seep through a crack that only heat and pressure will push water through.

                        I really like having the 4.3/ Didn't need the extra power really, since it is a fishing barge, but nice to add 15 MPH to the boat at significantly reduced noise level. Now instead of screaming along at 30 MPH not being able to talk without yelling, we cruise at 32 MPH and 3200 RPM with conversation level voices.

                        In the end all it cost was my labor as selling all the parts and pieces from the 3.0L drive system and parts left over from the donor boat paid for the swap.
                        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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