Small Merc 2 strokes- Cylinder head?

Discussion in 'Outboard Maintenance' started by Jacbo, Jan 4, 2010.

  1. Jacbo

    Jacbo Well-Known Member

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    So I had to take the water jacket cover of my newly acquired Merc 25 2 stroke (broke a bunch of bolts... different story.) and I noticed that it doesn't really have a cylinder head. This is kinda confusing for me as I've never seen a full sized engine without a cylinder head that's removable. So I guess you can't really blow a headgasket on one of these...

    Hmm, Just thought that was interesting.

    Pros- No more blowing head gaskets, Water intrusion into the cylinder due to leaky water jacket seals on HG.

    Cons- If you strip a spark plug hole, mess up combustion chamber somehow... You're screwed! :D
     
  2. noeettica

    noeettica Well-Known Member

    Naah if 'ya Strip threads clamp motor to a bench plug hole down set piston at BDC and feed compressed air into exhaust as helicoil tap cuts shavungs are blown from sp hole ... you have to go slow ... and also NOT drop tang from coil into cyl ...

    Dave
     

  3. Jacbo

    Jacbo Well-Known Member

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    Sounds like you've done this before! ;D
    Good Idea, Wouldn't have ever thought of that.

    I've done a little research on helicoil. Might end up being my only option cause I doubt I'm gonna have any luck with easy outs or the like for my broken bolts.
     
  4. noeettica

    noeettica Well-Known Member

    Take the motor to a machine shop with an EDM Machine and have them do the helicoil ... Dave
     
  5. noeettica

    noeettica Well-Known Member

    That's Funny My Motor has what looks like a Head ... That's just a water jacket cover ? ... AH Ha !

    What kind of gasket / O-ring ?

    Post a photo of yours ...

    [​IMG]
     
  6. Jacbo

    Jacbo Well-Known Member

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    Yea that's just the water jacket cover. That's why I thought it was interesting.

    Excuse the pic quality, It's dark and cold out there. ;D

    [​IMG]

    [​IMG]

    You can probably see the 5 broken bolts. :mad:
     
  7. noeettica

    noeettica Well-Known Member

    I would Definatly go for the EDM on those
    There is a thread here on Penatrating oils ... check with a local Merc guru They may have a "Drill Jig" for your motor a little heat and a lot of patiance are the key ... But Know when you are licked and when It's time to take it to the machinist ...

    I may check mine and apply never seize Since mine is a basically new motor ...

    You will not believe how long the Lower Unit Bolts are LOL ...
     
  8. Jacbo

    Jacbo Well-Known Member

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    Be careful! The bolts are imho way to small for the application and at least on my motor lower quality then I would expect from merc.

    My johnson is an '82 motor with just as much or more corrosion on it and I've broken only 1 bolt on the entire motor that I can think of... same spot though.

    About the broken bolts, What I'm gonna try is getting a SS nut tacked (TIGed) on to the top of each broken bolt. This basically gives me a new bolt head to work with but more importantly superheats the broken bolt without harming the threads (head applied only to SS bolt vs. heat applied to outside of block).

    I've read on some forums that this has worked well for other people.
     
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