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  1. #1
    Member
    Join Date
    May 2019
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    Miami, FL
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    27

    Question Thermostat cover, Helicoil or insert?

    Hello guys,

    2006 Mercury 115hp optimax - Serial 1B255833

    I was pulling the thermostat/poppet cover and a bolt snapped flush with the block. Punched, drilled it close to center and in my last pass with the 1/4 bit before switching to the thread tap I wobbled the drill and the bit snapped.
    After lots of swearing, frustration and more work I got the bit out but now I am left with a hole bigger than the original.

    I searched and read that in many areas helicoils are not recommended, but this being a part with no strength other than holding the cover flush would a helicoil do, or should I just bite the bullet and get an SS insert in there?

    I already have the helicoil kit, the other stuff I would have to buy.

  2. Member
    Join Date
    Jun 2013
    Location
    LONGVIEW TEXAS
    Posts
    11,176
    #2
    should work fine there , i hate salt water mtrs , good luck
    .................................................. ...the scariest thing in life is the unknown ...................................

  3. Member
    Join Date
    May 2019
    Location
    Miami, FL
    Posts
    27
    #3
    Thank you as always Joe.

    I had a hard time because the hole was a bit mangled but i got 2 helicoils stacked and was able to thread the original bolt back in there at the right torque.
    Used some aviation gasket sealer on the gasket and some tefgel on the bolts to avoid having to deal with this crap again. (at least on the thermostat cover)

  4. Member
    Join Date
    Mar 2005
    Location
    Shepherdsville Ky 40165
    Posts
    537
    #4
    Tefgel is good stuff.

  5. Member
    Join Date
    Dec 2021
    Location
    Biloxi, Ms
    Posts
    24
    #5
    Had that same problem with a motor that I bought. The original owner had mangled the bolt hole and did not install the thermostat on that bank. I cleaned out the bolt holes and installed 4 studs rather than using bolts. Now all that has to be done to remove the thermostats is remove the 4 nuts and slid the housing off the head.

  6. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
    Join Date
    Apr 2008
    Location
    Greenville, SC (US)
    Posts
    90,541
    #6
    Quote Originally Posted by Proline25 View Post
    Had that same problem with a motor that I bought. The original owner had mangled the bolt hole and did not install the thermostat on that bank. I cleaned out the bolt holes and installed 4 studs rather than using bolts. Now all that has to be done to remove the thermostats is remove the 4 nuts and slid the housing off the head.
    Cool idea- would work well on EFI models... many of the Opti's would be almost impossible to get the cover off the studs without removing other components.


    Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
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