Mercury Mark 5 gear case cover

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  • June 9, 2015 at 1:05 pm #1720
    archangel
    Participant

      I am working on a Mark 5 with a stuck L/U that was given to me. I have it all disassembled to the point of removing the gear case cover, but I am stuck. I have the correct tool to remove the cover, but it appears that someone attempted to remove it in some other way previously because the two holes for the tool pins are mis-shapen. Now the tool wants to ride up and out of the holes when I try to put enough torque on it to remove the stubborn gear case cover. I have sprayed it with Deep Creep and let it sit and I have heated it with a torch — though maybe not enough heat for long enough. I don’t want to exacerbate the problem by attempting to use the tool if it is only going to continue riding up and out of the receiver holes making them even more mis-shapen if the cover can be loosened more effectively by some means other than brute torque. Does anyone have any tips for dealing with this problem?

      June 9, 2015 at 1:10 pm #17844
      Buccaneer
      Participant

        US Member

        Is it right or left hand threads?

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        June 9, 2015 at 1:40 pm #17845
        archangel
        Participant

          Left

          June 9, 2015 at 2:06 pm #17847
          A Hoskins
          Participant

            US Member

            With the tool in place, install a small pipe sleeve over the prop shaft and install the prop nut kinda snug so the tool can’t rise. I would flood the O.D. of the cover with penetrant and apply just enough heat to the outside of the area to make the stuff boil. You could always drill another couple of holes and even if you go through, you can plug them. Easy does it.

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            June 9, 2015 at 2:20 pm #17849
            dave-bernard
            Participant

              US Member

              also redrill the holes to clean them up.

              June 9, 2015 at 2:22 pm #17850
              archangel
              Participant

                Unfortunately, the tool I am using is longer than the prop shaft (see the image in the first link), but I will try more heat and penetrating oil.

                http://www.johnsmcintoshvintagemercuryo … Mark6A.jpg

                Has anyone ever tried this for tough to remove threaded parts? Curious to know if it works at all.

                http://rustcheck.com/index.php?option=c … erosols-rp

                June 9, 2015 at 3:12 pm #17852
                archangel
                Participant

                  Thanks, everyone. I cut a piece of 1 1/2" abs plumbing pipe to fit down over both the cover and the tool snugly and it kept the tool straight so I was able to torque enough without it riding up out of the gear case receiver holes. Excellent ideas and advice as always!

                  Now I just need to get the drive shaft out. There was 40 year-old water in the gear case when the prop shaft came out so the rust is holding the drive shaft in nice and tight. Time for more heat and more penetrating oil, I guess.

                  Thanks, again!

                  June 10, 2015 at 9:31 pm #17939
                  dockbuster1
                  Participant

                    Lifetime Member

                    its a sad day when the pins break they are hardened and in a blind hole, so drill a line of 1/8 holes which allows the cover to collapse slightly and find a new or used one .that is how mercury recommends removing some of the newer gear cases

                    June 10, 2015 at 10:59 pm #17943
                    wiscoboater
                    Participant

                      Archangle,
                      If you find yourself in a situation like that again, try a bit of valve lapping compound in the holes. It works on stripped screw heads very well and might also work in this situation. In fact, it must work… Mumbles swears by it.

                      June 11, 2015 at 4:24 pm #17978
                      jeff-register
                      Participant

                        US Member - 2 Years

                        Did you remove the pinion gear bolt holding the drive shaft to the gear? It will not come out with the bolt in place.

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