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175hp cylinder walls and absurd compression results

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  • 175hp cylinder walls and absurd compression results

    Guys with more experience than me tell the compression readings I’ve been getting can’t be right: 60 psi on two cylinders, with the others showing 60 psi while cranking, but dropping to zero when I stop cranking.

    Word is that’s a bad gauge or I’m not using it right. But I got the same results with two different gauges. And it got 60 and held on some, but went to 60 and dropped on others. I was using the same gauges the same way each time. I’ve run compression tests lots of times on multiple engines. They’re kinyda hard to mess up. What could I be doing wrong?

    I pulled the heads and took pictures, which I’ll post below.

  • #2
    It has been clearly stated that a compression gauge only goes to zero when you push the release valve on the gauge.----They do NOT go to zero any other way.

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    • #3
      I wish I’d shot a video. All I can say is I watched it happen. I didn’t press the release valve, I just released the jumper switch that I was using to crank the motor. Time after time, two different gauges. I’m probably doing something wrong, but whatever it is, I didn’t press the release valve.

      Uploading photos now.

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      • #4
        Starboard lower

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        • #5
          Starboard center

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          • #6
            Well, I lost track of my labels, so I’ll have to re-shoot, or I won’t be able to tell them apart. Not my best work!

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            • #7
              Good idea !!

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              • #8
                Two bad gauges....or leaking ones
                You know that you are a very poor driver when Siri says : "In 1/4 mile pull over and let me out...."

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                • #9
                  The hole with the Siezco piston is worn out. Looks like it scuffed at one time and someone honed the crap out of it and slapped a new slug in der hole.
                  When in doubt,Trim it out!!!
                  Business Owner & Certifed Technician
                  Boats I own & use
                  20ft Javlin w/250 Junkrude
                  17ft Bullet w/200 Merc (SOLD!!)
                  13ft Allison w/150 I-6
                  17ft Hydra-Sport 175GT
                  15ft Allison w/75 Stinger(project)
                  14 x 48 Drifter with 1100SS Merc

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                  • #10
                    Originally posted by Faztbullet View Post
                    The hole with the Siezco piston is worn out. Looks like it scuffed at one time and someone honed the crap out of it and slapped a new slug in der hole.
                    So I’m looking at a rebuild, right? No way to repair just that one cylinder?

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                    • #11
                      Decisions are based on FACTS.-------I would run to a machine shop and MEASURE the cylinders with some degree of accuracy.----Then decide what needs to be done.----Post the numbers here.

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                      • #12
                        Originally posted by racerone View Post
                        Decisions are based on FACTS.-----.
                        Hmmm...You ever been married? 😏

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                        • #13
                          Good luck with your struggle on this motor.

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                          • #14
                            Originally posted by racerone View Post
                            Decisions are based on FACTS.-------I would run to a machine shop and MEASURE the cylinders with some degree of accuracy.----Then decide what needs to be done.----Post the numbers here.
                            Since it looks like I struggled to use a compression tester, I may be an unlikely candidate to get accurate cylinder measurements without outside intervention.

                            But I do have two ASE certified mechanics in the church where I serve. I’ll get their help and post the measurements, Lord willing.

                            Might take a while. Snow coming soon!

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                            • #15
                              Sign up today
                              MOD EDIT - A bit presumptuous to come from a 2 hour member.
                              Last edited by GA_Boater; January 14th, 2020, 07:22 PM.

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