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Replacing piston in a mercury xr2 175hp

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  • Replacing piston in a mercury xr2 175hp

    Hi-
    I originally was interested in replacing my 1997 xr2 sport jet power head after it died (and I started a separate thread on that subject, but now I am looking at repairing the engine instead.

    I found that one of the cylinders had piston damage (upper ring broke into 3 parts, and some of the aluminum piston was stuck between the head and the remaining portion of the piston top....The cylinder wall has aluminum mechanically welded to it (hone should remove that)...

    I have the head and intake manifold off the engine and I would like to simply remove the damaged piston and purchase a replacement (with new rings and rod bolts). I plan to spend quite some time honing the cylinder wall.

    I understand that I can simply unbolt the rod cap and push the piston up and out of the block. Unfortunately, I found that the rod bolts take a 12-point socket and most of my sockets are 6-point. I would take a run down to Sears and pick up the right 12-point socket if I knew the correct size. It appears that the correct socket size is smaller than 5/16".... Could these be metric bolts? I am hoping that someone here has knowledge of the bolt head size.....If so, I would appreciate if he would holler back and let me know what socket size I should get. Also, it appears that there isn't much room for excess socket thickness do to the small machined surface that the bolt head is up against.... so, I probably will need a thin-wall socket..
    Here are the pics of the damage:

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    Thanks in advance,
    Bob

  • #2
    Re: Replacing piston in a mercury xr2 175hp

    Not metric! It is a 5/16 and very thin wall. But tha bad news is that what your planning won't work. Might run a few minutes with that kinda repair but will not live long..........jmo

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    • #3
      Re: Replacing piston in a mercury xr2 175hp

      Originally posted by Dukedog View Post
      Not metric! It is a 5/16 and very thin wall. But tha bad news is that what your planning won't work. Might run a few minutes with that kinda repair but will not live long..........jmo
      Anybody else have any thoughts on the likelihood of success / or failure on just cleaning up the cylinder wall and putting a new piston & rings in it?
      I did this a long time ago with a corvette 327 engine and got almost 2 years of further life out of it before replacing it with a new 350 shortblock....

      I was really hoping that if I was careful honing out the cylinder wall, I would be OK....

      Thanks in advance

      Bob

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      • #4
        Re: Replacing piston in a mercury xr2 175hp

        That aint going to clean up and bein spec's, that a bore oversize....
        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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        • #5
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          Re: Replacing piston in a mercury xr2 175hp

          Bob, I have and still do tha hot rod chevy stuff but tha 2 stroke Merc/Mariner V6 is another story. It doesn't like outta whack tolerances plus tha fact that tha motor is full of debris from that clyinder that you cannot wash out without a tear down. Plus ya don't know if tha crank is hurt. Plus tryin' ta reinstall "cracked" top guided rods right through tha front half is a nerve wrackin' job for tha very experienced and sometimes takes "several' tries. Especially if ya don't know what ta look for after ya torque 'em. Just sayin.............D

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