Evinrude Sportwin bolt thread help needed

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  • thepetrolist


    Replies: 43
    Topics: 20
    #1189

    So guys, I started to tear down my ’63 10hp Sportwin I bought yesterday. I usually remove the cylinder head just to make sure everything looks ok, and to clean up every trace of old oil and so on. Well.. 3 out of the 10 cylinder head bolts snapped right off. Don’t know if I should laugh or cry right now 😆

    Anyway, does anyone know the thread on these bolt? I’m not that familiar with inch-based threads since here in Finland we mainly use metrics.. I tried to measure it and have found out that the closes match is a 1/4"x20 tpi UNC thread. Am I correct or completely wrong?

    Cheers
    Niko


    crosbyman

    Canada Member - 2 Years
    Replies: 3587
    Topics: 326
    #13853

    just take a good bolt taken out to match it at the hardware store.

    Joining AOMCI has priviledges 🙂


    thepetrolist


    Replies: 43
    Topics: 20
    #13858

    Yeah, of course, that’s the obvious thing to do but my OCD prevents me from accepting that it is just a bolt, I need to know the exact specs 😆


    phil

    US Member - 2 Years
    Replies: 199
    Topics: 19
    #13860

    Google SAE UNF threads. 1/4 by 19-20 will UNF rather than UNC. The F indicates fine thread, the UNC coarse threads.

    http://www.omc-boats.org
    http://www.aerocraft-boats.org


    fleetwin

    US Member - 2 Years
    Replies: 4737
    Topics: 46
    #13861

    OK, the head bolt threads on your engine are 1/4-20 UNC. Do you have access to a 1/4-20 tap? You may need to purchase a few 1/4-20 "helicoil" kits as well. These items can be easily found online if they are not available locally for you. The "helicoil kits" include the appropriate sized drill bit, one plastic helicoil insert driver/insert tool, and several 1/4-20 helicoil inserts.
    But, before we get to the helicoils, let me ask a few questions. Are the head bolts broken off even with the cylinder block deck? You may be able to avoid drilling out the broken stud if some of the broken bolt shank is sticking up from the block. Clamp the broken bolt stud with vice grips while heating the block/stud, once enough heat is applied, you may be able to gently rock the broken stud out with vice grips. Don’t force it, be patient, the broken stud will start to "rock back and forth" very slightly once enough heat is applied.
    If the bolts/shanks/studs are broken off even with the block, they must be drilled out. This is not an easy process, and success will depend on your skill level along with the quality of your drill bits. You may want to consider letting a machine shop drill out the broken studs if you have had little/no experience doing this type of thing.
    Post some pictures of your broken bolts here, that may help us find the best solution for you.


    phil

    US Member - 2 Years
    Replies: 199
    Topics: 19
    #13870

    Sorry, petrolist for some reason I got the idea you were talking about a pivot bolt on the transom clamp assembly. One thing that works well where you suspect that head bolts will break, is to cut or grind off the head of the bolt, remove the head casting, and weld nuts to the protruding shanks, this usually gets them hot enough to remove without breaking. A shot of your favorite penetrating oil onto where the threads start, to cool them a bit, will be drawn into the threaded area.

    Expect to have head bolts break wherever the motor has been run in salt water.

    http://www.omc-boats.org
    http://www.aerocraft-boats.org

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