Mercury Mark25 water pump service

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  • March 5, 2017 at 6:23 pm #6470
    fisherman6
    Participant

      US Member - 2 Years

      As you might guess by my YouTube channel I’m more of an OMC guy, but I do have a few Mercs in my collection to work on. I’m about to do the water pump on my Mk25, and I’m just curious if there is anything special I should know before I try to drop the lower unit. Thanks in advance.
      -Ben

      OldJohnnyRude on YouTube

      March 5, 2017 at 9:31 pm #53891
      david-bartlett
      Participant

        Ben,

        If you don’t have the Mercury manual I highly recommend you get one. I believe there is a copy on Garry’s Dropbox somewhere.

        Also lots of good info at Johns Old Mercury site.

        Carl’s folks have several special tools but a clever guy like you can make your own.

        I repeat, get the Manual # C-90-25500

        March 5, 2017 at 10:29 pm #53893
        david-bartlett
        Participant

          Ben,

          This is the one. Keep in mind it was written for trained Mercury repair people and may skip some steps that are understood to be there. Kind of like rules in Math.

          Read carefully and go slow. That Merc is a marvelous machine, but you need to treat it like a Merc, not an OMC.

          Attachments:

          March 6, 2017 at 12:10 am #53901
          fisherman6
          Participant

            US Member - 2 Years

            Thanks David, I will get a manual. I know it’s certainly not an OMC just from what little I have messed with it so far. That’s pretty much the story with any of my Mercs. Even the ones I have worked on. They are different animals from what I’m used to. They are kind of fascinating but I usually need OMC therapy after working on one.
            -Ben

            OldJohnnyRude on YouTube

            March 6, 2017 at 12:40 am #53905
            dave-bernard
            Participant

              US Member

              mark 25 pump is easy to do. 3 bolts drop the lower. put it in forward first. makes it easier to reinstall. the pump cover is right hand threads make a tool to remove. if you have a problem call me 1 914 three one zero 7086 Dave . or email me daveb409@hotmail.com.

              March 6, 2017 at 2:10 am #53916
              fisherman6
              Participant

                US Member - 2 Years

                Thanks Dave! That’s what I was hoping for. I figured I’d need to make a tool to remove the cover. Right hand threads and pUT it in forward before dropping the LU. Excellent! Thank you again. I’ll call you if I have any trouble when I get to it. It may be next weekend. I’m working on the water pump on my 1978 Merc 4hp now. New impeller a year ago and it stopped pumping. Impeller already had so much set it wouldn’t contact the sides of the pump housing. 😯
                -Ben

                OldJohnnyRude on YouTube

                March 6, 2017 at 5:57 pm #53945
                garry-in-michigan
                Participant

                  Lifetime Member

                  I think it’s really cool the way Dave has his dog trained to fetch books. . . 😆

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