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Blown head gasket

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  • Blown head gasket

    99% sure anyway. I had an older post about the boat making a weird noise, almost like air pushing past like a steam engine. At idle it was quiet, and this is my first boat and I just assumed it was normal. Everything else I build is loud as hell and you can't hear stuff like that!

    Anyway, I replaced the exhaust gasket and no change. Still could hear the noise, which was getting progressively worse under load, coming from the number 1 cylinder on the port side, sounded like it was coming from just above the alternator... so, right at the head gasket in other words.

    Did a compression test today, and every cyl is at 90psi except for that one, which is at 60. No bueno.

    Before I start tearing this thing apart, anything else I should consider first? I'll give the valve lash a look see while i'm at it, but I seriously doubt a valve tightened up to the point to let that amount of air past.

    *Boat is a 1987 Renken with a 2.5 Merc/Alpha One

  • #2
    Did a compression test today, and every cyl is at 90psi except for that one, which is at 60. No bueno.

    Before I start tearing this thing apart, anything else I should consider first? I'll give the valve lash a look see while i'm at it, but I seriously doubt a valve tightened up to the point to let that amount of air past.
    Ayuh,..... Welcome Aboard,.... You might have a rebuildable core motor,.... Those numbers should be more like 130 psi/ 150 psi,....

    Under 100 psi is a dead rebuildable core,....

    Comment


    • #3
      Well that's awesome news.

      It was a cold motor, for what it's worth. Head gasket was definetely blown in number one. Will order a new one tonight and put it back together.

      Comment


      • #4
        I would look for a free boat on craigslist with a 3.0 in it. (the free boats are usually listed as trailer, $300, must take boat, hull is rotten)
        1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

        Past Boats
        1970 Wooster Hellion - Merc 9.8
        2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
        1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

        What’s behind you doesn’t matter.Enzo Ferrari

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        • #5
          I paid $700 for this boat, including trailer. It's served us well. I'll replace the head gasket and keep beating on it, then pick something else up in the fall of next year.

          Comment


          • #6
            new head gasket wont change the fact that your motor is worn out and needs a rebuild.

            rebuilding or replacing the motor will change that fact.
            1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

            Past Boats
            1970 Wooster Hellion - Merc 9.8
            2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
            1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

            What’s behind you doesn’t matter.Enzo Ferrari

            Comment


            • #7
              It would be worth your while to do a leak down test before you pulled the head. May just be losing compression through the valves
              1999 Powerquest 260 legend
              502 mpi
              B1

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              • #8
                i did a leak down test. All is well, except for the #1 cyl, that as the blown out portion of the gasket. I stripped the head and it's at the machine shop getting cleaned and surface ground.

                There's not a chance on earth that I'm putting new pistons and getting the block bored and honed on a $700 boat that actually ran pretty darn god when it had a bad head gasket. If this was a boat I was planning on keeping for years, sure.

                *** comp test was done on dead cold engine, I was just using it to try and isolate the problem. I will check again when it's all put back together and do one at running temp.
                Last edited by Scott76; October 2nd, 2017, 10:15 AM.

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                • #9
                  Don't be surprised if that tired motor can not handle the higher compression of a new gasket & head job.

                  Seen more than one puke the bottom end afterwards. In fact, I have one sitting out back right now that's getting ready for a 4.3 swap because of that very thing.

                  Don't get me wrong, I don't blame you for not throwing good money after bad. But, it could be that's what you've just done. Those are relatively cheap to overhaul if it comes to that though. Well, parts are not as cheap as a small block but they're not terribly expensive to build.

                  Good luck with it either way.
                  Jim.

                  Comment


                  • #10
                    Hmm, that is an interesting point.

                    I'm gonna continue down this path, if it grenades, it grenades. I like working on stuff anyway. The season is all but over here in Wisconsin anyway.

                    4.3 swap sounds interesting.... any details or a link?

                    Machine shop called today, mangaflux of the head came back good. He was surprised, said the vast majority of 2.5/3.0 heads he gets are cracked.

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                    • #11
                      How could your leak down test be fine and all is well when your psi is 90 ?
                      1999 Powerquest 260 legend
                      502 mpi
                      B1

                      Comment


                      • #12
                        Because it met my standards for a $700 boat, and held that PSI for some time? Are you confusing leak down and compression tests?

                        I get it - those are low PSI readings. Again - it was performed on a motor that was dead cold. Do I expect it to rise to 150 when warm? No. Do I expect to yank a motor and do a complete rebuild on a 700 dollar Renken bowrider because the comp test read a little low? Give me a break, that **** is ridiculous. Just FYI, this is not the firstt time I've been inside of a motor.

                        By all means, continue to tell me I should dump more cash into this boat.

                        Comment


                        • #13
                          A leak down test doesn't hold psi. You feed 100 lbs. of air steadily into the cylinder and on the other gauge it will tell you how many pounds the cylinder will hold. while it's actively being fed the constant 100 psi

                          So then the leakdown rate is measured as a percentage. So not sure what your talking about when you say it held PSI for some time.
                          1999 Powerquest 260 legend
                          502 mpi
                          B1

                          Comment


                          • #14
                            Sign up today
                            Originally posted by Scott76 View Post

                            By all means, continue to tell me I should dump more cash into this boat.
                            I'm with ya on that...sometimes it's worth just doing a patch job on something you do not expect much out of.

                            As long as it's safe and secure run that bad boy till it fails.

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