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mercury 70 hp 2 stroke outboard rebuild advice

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  • mercury 70 hp 2 stroke outboard rebuild advice

    hi guys
    just looking for a bit of information and advice.
    i am new to the site so hopefully this makes sence haha.

    ok i have just bought my first boat which has a old 70 hp 2 stroke 3 cylinder outboard.
    i am looking to rebuild it or at least get a bit of information.(just engine at this stage)

    i am an engine builder by trade but have had very little to do with outboards especially 2 strokes.

    so what i was wondering is firstly does anybody have engine specifications (with full tensions,piston over sizes,crankshaft sizes etc) or does anybody know where i could find them. even engine diagrams

    and also could anybody direct me with gasket kits,bearings or just anything you could suggest i would need.

    or just generally any advice.

    any help would be greatly appreciated

    thanks in advance

    clint


  • #2
    Re: mercury 70 hp 2 stroke outboard rebuild advice

    Clint;

    Do you have the s/n of the engine?

    Gerry

    Comment



    • #3
      Re: mercury 70 hp 2 stroke outboard rebuild advice

      Originally posted by carholme View Post
      Clint;

      Do you have the s/n of the engine?

      Gerry
      Hi Gerry thanks for replying. the serial number is 4572172.

      Comment



      • #4
        Re: mercury 70 hp 2 stroke outboard rebuild advice

        so what i was wondering is firstly does anybody have engine specifications (with full tensions,piston over sizes,crankshaft sizes etc) or does anybody know where i could find them. even engine diagrams
        Piston over sizes are .015 and .030 other sizes are available but it don't suggest that brand. What crank speck ya looking for? Check cylinders for taper as all inlines wear around the ports.
        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

        Comment



        • #5
          Re: mercury 70 hp 2 stroke outboard rebuild advice

          Originally posted by rammed wx View Post
          hi guys
          just looking for a bit of information and advice.
          i am new to the site so hopefully this makes sence haha.

          ok i have just bought my first boat which has a old 70 hp 2 stroke 3 cylinder outboard.
          i am looking to rebuild it or at least get a bit of information.(just engine at this stage)

          i am an engine builder by trade but have had very little to do with outboards especially 2 strokes.

          so what i was wondering is firstly does anybody have engine specifications (with full tensions,piston over sizes,crankshaft sizes etc) or does anybody know where i could find them. even engine diagrams

          and also could anybody direct me with gasket kits,bearings or just anything you could suggest i would need.

          or just generally any advice.

          any help would be greatly appreciated

          thanks in advance

          clint
          Hi guys i also have an mercury 70 hp 2 stroke 3 cylinder outboard and was looking for engine spec and any other information or maunals

          thanks

          Comment



          • #6
            Re: mercury 70 hp 2 stroke outboard rebuild advice

            Originally posted by Faztbullet View Post
            Piston over sizes are .015 and .030 other sizes are available but it don't suggest that brand. What crank speck ya looking for? Check cylinders for taper as all inlines wear around the ports.
            ok great news. so it is possible for a bore and hone with out sleeve replacement.
            crank specs i am looking for are standars sizes for big ends and mains and if you can grind them if worn for undersize bearings.
            basically thats why i need specifications and sizes to measure and inspect everything to see what is reconditionable and avaliability of pistons bearings etc.

            thanks alot

            Comment



            • #7
              Re: mercury 70 hp 2 stroke outboard rebuild advice

              Clint;

              Your s/n comes up as:

              70 70 3-cyl 4571652 4825848 1977 USA

              From here:

              http://www.marinshopen.se/Motorer/Om...6/Default.aspx

              Parts Listing:

              http://www.crowleymarine.com/mercury-outboard/479.cfm

              Service Manual P/N: 90-86135--5

              http://www.ebay.com/itm/USED-93-Merc...-/270801861441

              In the interim until you get a Merc manual, here is a link to the condensed version of the Clymer manual. Let the page load for several seconds and then download soonest to your computer as the link is short lived.

              http://web.ebscohost.com/serrc/pdf?s...4&vid=4&hid=11

              Gerry

              Comment



              • #8
                Re: mercury 70 hp 2 stroke outboard rebuild advice

                i am looking for are standars sizes for big ends and mains and if you can grind them if worn for undersize bearings.
                Nope..... bearings only come in one size and in over 40+years of wrenching never see a worn out crank as everything internal is roller/needle bearings.
                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

                Comment



                • #9
                  Re: mercury 70 hp 2 stroke outboard rebuild advice

                  Originally posted by Faztbullet View Post
                  Nope..... bearings only come in one size and in over 40+years of wrenching never see a worn out crank as everything internal is roller/needle bearings.
                  thanks alot.

                  Comment



                  • #10
                    Re: mercury 70 hp 2 stroke outboard rebuild advice

                    Originally posted by carholme View Post
                    Clint;

                    Your s/n comes up as:

                    70 70 3-cyl 4571652 4825848 1977 USA

                    From here:

                    http://www.marinshopen.se/Motorer/Om...6/Default.aspx

                    Parts Listing:

                    http://www.crowleymarine.com/mercury-outboard/479.cfm

                    Service Manual P/N: 90-86135--5

                    http://www.ebay.com/itm/USED-93-Merc...-/270801861441

                    In the interim until you get a Merc manual, here is a link to the condensed version of the Clymer manual. Let the page load for several seconds and then download soonest to your computer as the link is short lived.

                    http://web.ebscohost.com/serrc/pdf?s...4&vid=4&hid=11

                    Gerry
                    thanks gerry

                    Comment



                    • #11
                      Re: mercury 70 hp 2 stroke outboard rebuild advice

                      Has anybody built one of these engines before as I would be interested to know what they have done in terms of performance modifications

                      Comment

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