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  1. #1
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    Stripped spark plug threads

    2010 Mercury 250 pro xs. Serial # 1B751217
    I was attempting to change my spark plugs today when I found a couple spark plug holes to be cross threaded. I got the old plugs out but cannot get new ones in. I feel comfortable chasing the threads with a back tap or regular spark plug tap. My question is how involved is removing the heads to ensure no metal shavings get in the cylinders? Or is this necessary at all? It looks pretty straight forward to me but I’m sure I’m missing something. Do you have to replace gaskets, o rings, & bolts when you re-install it? Thanks in advance.

  2. Member
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    #2
    IMO a new head is relatively inexspensive and easy to RR. One of the beaties of a 2 cycle engine. Would need head bolts, head orings and thermostat gasket.


    Quote Originally Posted by swimjig180 View Post
    2010 Mercury 250 pro xs. Serial # 1B751217<br>
    I was attempting to change my spark plugs today when I found a couple spark plug holes to be cross threaded. I got the old plugs out but cannot get new ones in. I feel comfortable chasing the threads with a back tap or regular spark plug tap. My question is how involved is removing the heads to ensure no metal shavings get in the cylinders? Or is this necessary at all? It looks pretty straight forward to me but I’m sure I’m missing something. Do you have to replace gaskets, o rings, &amp; bolts when you re-install it? Thanks in advance.
    Last edited by leo13; 03-14-2018 at 03:45 PM.

  3. Member
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    #3
    Now would be a good time to send injectors (air and fuel) and rails to Don for cleaning. Just saying.







  4. Kllr bee
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    #4
    To get a good outcome I would take head off and put heli-coils in the cross threaded plug holes. If you try to just chase the threads you may have a plug exit through the cowl.
    Richard

  5. Member
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    #5
    I don’t know if stripped is the right way to describe these threads. They are just damaged on one side. Looks to me like they just need to be re-traced.

  6. Member
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    #6
    If you can SEE damaged threads, then the head will need inserted, or replaced.



  7. Member
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    #7
    I had one hole that presented the same way when I went reinstall the plug. I installed a heli coil after cleaning up the threads. So far so good . I have probably run it 3 or 4 hours since then. 2013 250 Pro XS
    GETFISHED !!!

  8. Member
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    #8
    I would use a TIME-SERT, not a Heli-coil.



  9. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #9
    Quote Originally Posted by Savage View Post
    I would use a TIME-SERT, not a Heli-coil.
    +1


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  10. Member
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    #10
    Ok. I didn't know about that. Should I remove
    the heli coil and put in the other or not . Not currently experiencing any negatives after getting the plug installed.
    GETFISHED !!!

  11. Member
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    #11
    I would chase it with a plug tap with grease on it a little at a time. Check the threads with a light and magnifier. Put the plug in and see if they are loose. If not, torque it (with a torque wrench) and run it.

  12. Member
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    #12
    Quote Originally Posted by TrackerPro16 View Post
    I would chase it with a plug tap with grease on it a little at a time. Check the threads with a light and magnifier. Put the plug in and see if they are loose. If not, torque it (with a torque wrench) and run it.
    This did not work. i am beyond that. Hence the Heli-coil. Just wondering if I need to remove it and install the suggested Time-Sert. The Heli coil appears to be working fine. I didn't know about the Time- Sert until I had already installed the Heli Coil.
    GETFISHED !!!

  13. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #13
    Quote Originally Posted by getfished View Post
    This did not work. i am beyond that. Hence the Heli-coil. Just wondering if I need to remove it and install the suggested Time-Sert. The Heli coil appears to be working fine. I didn't know about the Time- Sert until I had already installed the Heli Coil.
    Personally I would not EVERY use a HeliCoil in an Optimax cylinder head. Time-Serts, or Sleeves are great (provided you have the right tool to thread the head for the sleeve).

    If it were mine- that's how it would get fixed. Sleeve it once and "done".


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
    Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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  14. Member
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    #14
    Both work Ok if done correctly. Time Sert is better.