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Seized 25hp 2-stroke

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  • Seized 25hp 2-stroke

    My brother acquired a 25hp 2stroke mercury that is apparently only a few years old (don't have the year) and has very low hours on it. Someone ran straight gas in it and it's seized. I've tried dumping oil down the spark plug holes, still not freeing up with the pull rope.

    Question is should I try turning the crank with a wrench or just pull the head and see if the cylinder will come off the pistons??

    We are hoping that a bore and some new pistons will bring this motor back to life. Are we wasting our time? Lower end spins just fine.


  • #2
    Re: Seized 25hp 2-stroke

    You will have to tear down the power head to ascertain where the seizure is. It could well be in the bores as you say but it may also be at the crankshaft main shells..If it is seized at the crank and has any bad scores in the barrels you would be best off finding another motor tbh.

    LLB
    Kermit Klein fashion guru to the stars...

    Pearly Miss 12 ft aluminium boat (1959)
    Hornsea peble 13ft

    Mariner 8M (1982)
    Mercury 2.5 hp direct drive(1992)
    Johnson 15 hp commercial (1999)
    Seagull 4hp (1972)
    Tomos 4.5hp (1978)

    Comment



    • #3
      Re: Seized 25hp 2-stroke

      Originally posted by xjma View Post
      My brother acquired a 25hp 2stroke mercury that is apparently only a few years old (don't have the year) and has very low hours on it. Someone ran straight gas in it and it's seized. I've tried dumping oil down the spark plug holes, still not freeing up with the pull rope.

      Question is should I try turning the crank with a wrench or just pull the head and see if the cylinder will come off the pistons??

      We are hoping that a bore and some new pistons will bring this motor back to life. Are we wasting our time? Lower end spins just fine.
      Yeah plus the stopped making 2 strokes in 2006 or 2007, so it has to be at least 5 years old.....
      16' Starcraft Restoration
      http://forums.iboats.com/boat-restor...on-589808.html

      - Pete

      Comment



      • #4
        Re: Seized 25hp 2-stroke

        Originally posted by Lubosleftboot View Post
        You will have to tear down the power head to ascertain where the seizure is. It could well be in the bores as you say but it may also be at the crankshaft main shells..If it is seized at the crank and has any bad scores in the barrels you would be best off finding another motor tbh.

        LLB

        How likely is it to have seized down on the crank bearings??? I'm hoping cylinders!!

        Comment



        • #5
          Re: Seized 25hp 2-stroke

          What is the s/n of the engine and why not tear it down anyway? You own it and may get lucky. Nobody can say what the problem is until you get it apart.

          Gerry

          Comment



          • #6
            Re: Seized 25hp 2-stroke

            RIght even if you part it out it will make you more $ than a parts motor.
            16' Starcraft Restoration
            http://forums.iboats.com/boat-restor...on-589808.html

            - Pete

            Comment



            • #7
              Re: Seized 25hp 2-stroke

              Depending on the year it may be a scrap out motor. Only the blocks with the words Mercosil casted on the block is boreable if not it is a chrome bore and will need to be resleeved..
              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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              • #8
                Re: Seized 25hp 2-stroke

                where would I find the 'mercosil' cast?? Are sleeves available??

                I don't know much about the motor other than it's got low miles, merc 25 stroke outboard with electric start and some kid that temporarily worked at my brothers job ran straight gas in it and seized it. It's been sitting around since then and despite his work having tons of boats and motors of all shapes and sizes, nobody there knows how to tear into them, so they just buy a new one. When I saw it it was ofcourse dusty but I would guesstimate based on looks of the housing that it is early 2000s ish vintage. Apparently it was on a boat that nobody liked to use.

                I'll have to get the numbers off of it this weekend. I guess I'll just start tearing it apart and see what I find. Other than the lower end, what parts would be useful to people?? I guess if it's Fed the block could make a decent anchor for a jon boat or something, haha.

                Comment



                • #9
                  Re: Seized 25hp 2-stroke

                  You can replace the powerhead, if you want to keep the motor, and use the needed parts from the old one. Check out the list of salvage yards listed on here, or ebay. If stright gas and no oil was used, the crank, bearings, pistons, and block are probley shot and can be sold along with the alluminim (SP) cans you collect while working on it. Isn't life grand Tee Hee. That way you will get some of your money back.Check out outboardexchange.com for a powerhead.
                  Oldman570

                  Comment



                  • #10
                    Re: Seized 25hp 2-stroke

                    Originally posted by oldman570 View Post
                    You can replace the powerhead, if you want to keep the motor, and use the needed parts from the old one. Check out the list of salvage yards listed on here, or ebay. If stright gas and no oil was used, the crank, bearings, pistons, and block are probley shot and can be sold along with the alluminim (SP) cans you collect while working on it. Isn't life grand Tee Hee. That way you will get some of your money back.Check out outboardexchange.com for a powerhead.
                    Oldman570
                    With all due respect Oldman, I really do hope that you're wrong about the crank bearings, but I guess there is only one way to find out!! If the crank itself is fine (lower rod bearings OK) then it still shouldn't be too bad to fix.

                    Keep in mind the total cost into this motor so far is zero, so throwing 500 bucks of parts at it is still a good deal to for us (my brother and I). I enjoy working on motors, when I have the time.... This is just a 'hey, we can get this otherwise mint motor that is seized up for free, think it's worth messing with?' deal.

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                    • #11
                      Re: Seized 25hp 2-stroke

                      Originally posted by xjma View Post
                      With all due respect Oldman, I really do hope that you're wrong about the crank bearings, but I guess there is only one way to find out!! If the crank itself is fine (lower rod bearings OK) then it still shouldn't be too bad to fix.

                      Keep in mind the total cost into this motor so far is zero, so throwing 500 bucks of parts at it is still a good deal to for us (my brother and I). I enjoy working on motors, when I have the time.... This is just a 'hey, we can get this otherwise mint motor that is seized up for free, think it's worth messing with?' deal.
                      Well he is saying that if oil wasnt used, then your s.o.l. Hopefully someone just ran the motor with a blown waterpump and the pistons seized up, but the crank is fine.
                      16' Starcraft Restoration
                      http://forums.iboats.com/boat-restor...on-589808.html

                      - Pete

                      Comment



                      • #12
                        Re: Seized 25hp 2-stroke

                        My brother is pretty convinced that some 'summer help' didn't know the difference between 2 and 4 stroke and ran straight gas in it .

                        I know that with other 2strokes, straight gas doesn't necessarily mean the crank will be toast....I'm hoping here!!!

                        I really hate separate injection systems but in this case maybe it would have been better off....but then again, then I wouldn't be getting the whole outboard for nada.

                        Comment



                        • #13
                          Re: Seized 25hp 2-stroke

                          Depending on what block you have, you could be in good shape. Blocks with chrome bores can not be bored out and have to be replaced if the bore is to scored real bad. You can sometimes lightly scrape the ammumin off a chrome bore and hone it and replace the pistons only if the crank and rod bearings are good. As for the oil injection, I would disconect it and use premix gas. That way you know it will get oil as the oil injection can and will go bad and you'll be back to square 1 again. Like I stated before, it is sometimes cheaper to just replace the power head with a good used one from one of the salvage yards. A good used powerhead shouldn't cost very much, as most dealers would rather sell new motors, rather than fix the older one and sell it, if the motor is 10 years old. At any rate the powerhead will have to come off and be split inorder to check the crank and bearings. Now you have a spring project, to keep you busy in your spare time, and you can end up with a motor that will last several years when done correctly.
                          Best of luck and Boating,
                          Oldman570

                          Comment



                          • #14
                            Re: Seized 25hp 2-stroke

                            I think they were running pre-mix in this one...which is how the kid that didn't know ended up running straight gas. I prefer pre-mix too, except for on snowmobiles.....hard to mix at a gas station.

                            Comment



                            • #15
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                              Re: Seized 25hp 2-stroke

                              Originally posted by Faztbullet View Post
                              Depending on the year it may be a scrap out motor. Only the blocks with the words Mercosil casted on the block is boreable if not it is a chrome bore and will need to be resleeved..
                              So the motor is now in my back yard on a stand and ready for me to tackle it once I get the time. It's a 1998 model year, and the block says 'mercosil' so I guess it's boreable, which is a plus!!

                              I would do pretty much all the work myself other than bore/hone and redoing the actual crank and rods if that is necessary I'd have an experienced machine shop do that and balance it, etc. but other than that I can work on motors. It is a little different than a dirt bike or ATV motor....some of the **** I'm like, what is that, but I'm sure I'll figure it out once I rip it apart. Speaking of which I think I'm going to go pull the head off of it right now, so wish me luck fellas!! Thanx for all the help so far!

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