Home Forum Ask A Member Mark 5 gear house casing cracked

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  • #6200
    cheetahgod
    Participant

      I’m trying to get this old mark 5 up and running. There is a crack in the gear house. Can this be fixed or is it better to get a new one?


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      #51826
      fisherman6
      Participant

        US Member - 2 Years

        Those cases are very thin and the water pump is inside. That looks like a freeze crack to me. I may be wrong but it would seem difficult to repair properly. I would look for a replacement.
        -Ben

        OldJohnnyRude on YouTube

        #51831
        green-thumbs
        Participant

          US Member - 2 Years

          OOPS (Mark 5 Gear Housing is 1607 400 A2 same as Mark6 and Mark6A per )
          Not uncommon problem. I would suggest picking up copy of 1965 and Prior Mercury
          Service Manual AND Parts Manual for Mark 5
          It looks like you are going to have an educational experience.
          Service Manual are around used reasonable
          Parts Manual may be on line at Western New York Chapter.
          Good Luck
          Good Thing Sharper Minds and Eyes are around to point out sloppy thinking.

          #51835
          cheetahgod
          Participant

            Found the parts manual online and printed it out.

            #51838
            20mercman
            Participant

              US Member

              The Mark 5 is a wonderful motor, and a real performer for it’s 5 hp. class, but this is the largest and most common issue with them! The gear cases are very prone to water intrusion, and this is what happens. I have seen a ton of these with this problem, and I have a case that I have welded up now. I am still working on getting the threads repaired after the welding, as you need penetration to get a good weld, and this usually damages the threads. This is a left hand thread housing, and they are hard to come by. As you still have the broken off part, take it to a sheet metal shop that does aluminum work and see if someone will weld it for you, but be wary of the risk to the threads. If you can find another housing, that is the best option, but it is not always something you can find, as like I said, the Mark 5 and Mark 6 use the same basic housing and they are all prone to this damage.

              Steve

              #51844
              dave-bernard
              Participant

                US Member

                sorry to say, but the KF5 and Mark 5 have different gear cases. the mark 5 has a neutral shift and pump is on the drive shaft not the prop shaft. the crack is from the drain hole being blocked, and the water freezes. it can be repaired.

                #51849
                cheetahgod
                Participant

                  The pull start seems difficult to pull compared to my other outboard. Do I just need to grease the parts or put some oil in the cylinders ?

                  #51854
                  fifty20ne
                  Participant

                    US Member

                    In an old Antique Outboarder magazine I read an article on how to repair this type of freeze crack by
                    grinding material back behind the prop. I don’t have the article at home as I left it in my desk (toolbox)
                    at work. I can scan it for you next week or maybe someone else can look for it there collection and
                    post it.

                    Good Luck,

                    Bob

                    #51859
                    cheetahgod
                    Participant

                      There’s a brand new gear casing unit on eBay ATM for $100 us. I’ll post in the classifieds after I check the compression when my tester comes o Sunday.

                      #51861
                      dave-bernard
                      Participant

                        US Member

                        That is the one. note the spacer and instructions. good find.

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