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NEED HELP.. Hole in top of Cylinder Crankcase

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  • NEED HELP.. Hole in top of Cylinder Crankcase

    Hey Guys,
    I went out for a run on Sunday and my 2002 70hp 2 Stroke was struggling.
    It would happily cruise at 2000rpm but when i opened it up it would struggle.
    It would go from 3000 3500 4000 then drop to 3000rpm never consistent.

    I put in new fuel water separator, fuel filter and spark plugs back in early February.

    I got it home and checked the spark plugs and the plug in No#3 looked terrible and seemed to be wet

    So i decided to take the head off and have a look at the gaskets to see how they looked.

    After i got the head off and the cylinder head cover I noticed on top of the crankcase was small hole.It looks like it has been repaired before (Pic2 & 3)

    Can anyone tell me if this can be repaired again using JB Weld ?
    or will i need to get a new crankcase.

    Would this have been the cause of the engine run rough? Spark Plug / Water in cylinder?
    Any help would be grateful

    Last edited by Stuy1980; 05-17-2017, 03:34 AM.

  • #2
    Looks like rust on the plug, and steam cleaned head, yup, water intrusion. Can it be repaired? I wouldn't put any money in it. And yes, that certainly is the source of the sluggishness. Can't burn H2O.


    • #3
      Can it be repaired with JB weld again? Maybe.Will it last and be reliable, no.

      Another good used block would definitely the way to go if you really want to fix it right.

      Probably not worth the time, energy and money to repair properly. But that is up to you.


      • #4
        the hole is on top of #1 going to the outside not into the cylinder.

        Water into #3 did not come from there unless it was being sucked into the #3 carb

        A good welder might be able to fix it


        • #5
          #1 and #2 are getting steam cleaned by water intrusion. Looks to me like #3 is just starting to get water looking at the picture of the head. I suspect that head is warped . Surprisingly a brand new head is $220.00.

          The block is the problem. By the time you grind all that corroded area out to get back to something clean enough to weld to...well who knows. If that went well, then the block would have to be decked off flat in a milling machine. It would need to be totally disassembled for that to be done.

          A lot of time and money to fix it right...IMO


          • #6
            Maybe locate and purchase another motor very similar in model and year to yours....keep your old corroded motor for spare parts?...


            • #7
              For the hole, I would bring the block to a prop shop and see about TIG welding a new small piece in there. (They weld very thin aluminum props, so your block wouldn't be bad).

              The weld is way on the outside, not near the cylinder so it not quite so critical as if it was at the cylinder itself.

              How the water is getting into the cylinders is the question of the hour.

              Did you inspect the head gasket closely? You'll need to find that water point of entry.

              Being two adjacent cylinders are sucking water, I'd strongly suspect the head gasket... At least focus your inspection between those 2 cylinders/head.

              Now, if you have numerous thin spots of corrosion thru out the engine
              (very possible), the block may not be worth fixing.

              __________________________________________________ _____________

              Just as a side note, I was given a Mercury (70 HP maybe) MANY years ago.
              It rotted out at the very top of the combustion chamber into the water jacket.

              The largest area(adjacent to the combustion chamber) was approx 1/4" and expanded out larger towards the water jacket. Cleaned it up, made up a plug to fit and had it TIG welded. Motor ran great after that.
              Bought another hull and sold both!

              1997 Angler 204 CC, 2006 F150 TXR


              • #8
                Thanks for the info guys much appreciated.
                I'll have a closer inspection of the head gasket tomorrow and see if I can find the water entry point.
                I'll also take it to the shop to get another opinion and price to fix.
                If I was to get another 2nd hand powerhead. Is it hard process to swap things over.? I can do basic mechanic work but am not that advanced.
                More Pics for reference

                Last edited by Stuy1980; 05-17-2017, 09:35 AM.


                • #9
                  JUST for curiosity, I would clean the mating surface of the cylinder head (gasket surface) and hold it to something known flat, like the wife's glass coffee table top, or a plate glass window to see if the head is warped.

                  Yes, consider that if that one spot has corroded through, what is the wall thickness of the rest of the cooling passages...

                  Now it could be resultant of a habit of how the engine is put to bed. Corrosion is oxidation. Possibly this engine has been leaking hydrocarbons past the head gasket into the water passage. Burned hydrocarbons and water often result in hydrochloric acidity. Lets say that this engine is tilted and stored with the powerhead leaning to the one side and that is where an air pocket forms over years and years. Possibly, this is the only place where the deterioration is greatest and a repair may be worthy.
                  If its got teats or tires, you bound to have trouble with it....


                  • #10
                    Clean it all up and see what it looks like...pick that JB weld off. Sometimes it looks worst than it is. The pictures are great.


                    • #11
                      So i picked the JB Weld off and you were right (panasonic)
                      It is worse than first expected.
                      The hole is bigger than first thought and another hole was found just above thermostat housing..Also the top of the block where head connects seems to be worn in places so im guessing this was the water entry point.

                      Now question is if I buy a second hand block what is the process of changing it all over? Would I be able to do this myself with basic tools and no real workshop.?
                      I will go and see the local shop and get there thoughts and hopefully a price

                      But im pretty sure this block has had it.

                      I cant really afford a new motor at the moment so what ever I can do myself to keep costs down as I will have some time in the coming weeks.

                      Any input would be appreciated.


                      • #12
                        Long Block

                        I would, as previously suggested, try to by a similar engine and keep yours for a parts spare. Lower unit strips out after a month, no worries, I have a spare... Carburetor acting up, swap them out...

                        When you find one that you are considering, bring a small, light weight, ball pien hammer, and tap around these same spots. you will be able to tell with some certainty if the metal in these area's is solid or dead sounding (being corrosion layers encapsulated in paint and JB weld.
                        If its got teats or tires, you bound to have trouble with it....


                        • #13
                          Sorry buddy that block is done, in my opinion
                          If there are that many holes showing, there are more hiding from you. If you patch the holes I think you will have trouble getting your head gasket seal as well due to the corrosion I can see in your pictures...

                          If you can get another power head with crank and pistons that would be best. A empty block will be a pile of work, journal bearings, seals, gaskets, etc. Probably cheaper to find a used complete motor and use yours as a spare parts donor.

                          I don't know what else to say...sad to see its in such bad condition.


                          • #14
                            Plus 1 ^^^. Way too many holes, super thin material left and that's JUST what you can see.

                            If you can pick up a re-manufactured long block (if the engine is even worth it) would likely be the way to go.
                            1997 Angler 204 CC, 2006 F150 TXR


                            • #15
                              Thanks for all the info guys. Much appreciated..
                              Only plus side is it's coming into winter here. So I've got some time up my sleeve to work on the boat itself and save some coin..
                              Cheers all👍