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This is to DakotaMan, I hope that the outboard rebuild is still going OK. The small bolts around the head area just hold a water

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  • This is to DakotaMan, I hope that the outboard rebuild is still going OK. The small bolts around the head area just hold a water

    This is to DakotaMan, I hope that the outboard rebuild is still going OK. The small bolts around the head area just hold a water cover on and will most probably need heat to remove them. You can drill out any that you have broken off but be sure to try to hit the center of the bolt and step up in drill sizes until you are close to the tap size drill. Most of the bolts will be 1/4- 20 and the most common tape drill size for them is a #7 drill. If you start with a 1/8 drill and then go with a 3/16 LEFT HAND drill you just might screw out the broken off screws during the drilling process. But if not, you still have room to drill with the #7 drill and retap. If the threads are completely wiped out, you can heli-coil them. Good luck.

  • #2
    Thanks for thinking of me Santa... your advice has been most helpful so far. I'm going kind of slow due to lack of tools. I had to get a cylinder hone and new torque wrenches. Now I'm waiting for a cylinder gauge so I know for certain whether I will need oversize pistons. I don't think I will but can't really measure very well down inside the cylinder yet. That tool should be here in a day or two and then I can order the pistons. I am planning to use the same rod bearings on the crank side since I just had the power head re-built about 150 hours ago... I don't think I ran it long enough to damage them... what do you think? I will need to find a 12-point thin walled socket if I take that end of the rod loose since I don't have anything that will fit it in my tool box. Thanks again.


    • #3
      Oversize pistons should not be necessary with the two stroke engine. But if you decide to go with an oversize piston in just one bore, it will work just fine. Two stroke mercs do not depend on piston skirt clearance as much as four stroke engines and the rings do not have to scrap oil back into case so you can get by with a different line of thinking in terms of grooves and scratches in the bores. Also the engines are not very well balanced so slight differences in bores and piston weights do not matter under normal use. If the needle bearings on the crank are slightly blued then they could have been run slightly starved for oil and need to be replaced, but if they are still brite then they should be OK. Also check the reed plates before reassembly. To drill out the 1/4-20 broken screws, I suggest starting with a #2 or #3 center drill and then drilling with a short screw machine 135 degree spilt point 1/8 drill. Jobber length drills will bend and drill off to one side too easily. Once you have drilled a hole all the way through the old screw, then fill the hole with a good prenetrating oil and let it sit for a while. Then try a 115 degree 3/16 left hand drill bit to drill and back the screw out. All these drills are very common and can be supplied from companies such as MSC over the net.


      • #4
        Thanks again Santa. Your help has been indispensable. I got my cylinder gauge and the cylinders are right on standard cylinder size. They looked like they were really scratched but apparently it was just aluminum glaze from the pistons. Once I honed that out and stopped at the steel cylinder sleeves they were right on at 2.875 all the way through so I can use standard pistons. Now I'm worried about whether I will be able to compress the rings with my fingers since I didn't remove the crank from the head (I'm trying to save myself some time). I will check the reed plates... my shop manual explains how to do that. I will also get the drill bits and drill out those broken bolts... thanks again.




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