magneto cam installation

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  • Carlasdaddy

    Replies: 13
    Topics: 9

    So far I have split 2 of these cams trying to install on a 1956 model 10012 10hp Evinrude. I wedged open both points to make clearance and installed crank key parallel to taper. Any advice for the next one?. Photo is attached.


    • This topic was modified 1 month, 1 week ago by Carlasdaddy.
    • This topic was modified 1 month, 1 week ago by Mumbles.


    US Member - 2 Years
    Replies: 4062
    Topics: 41

    Hmmm, that is peculiar…. Are you forcing the cam down with a hammer/socket?
    Are you sure you have the right cam/crankshaft key?
    I guess I would remove the mag plate/upper seal components at this point and have a closer look at the crankshaft. That key should slide down onto the crank with little or no effort, if not, something is wrong…..


    Canada Member - 2 Years
    Replies: 5174
    Topics: 276

    Try the next one with the key parallel to the centerline of the crankshaft and see what happens. It’s a bit tricky to do but the key must be fully seated in its groove and the cam should slide easily over it. You may have to remove the mag plate to seat the key properly. After reseating the key, remove the cam and make sure the flywheel is bottoming out on its taper to. It may take more than one attempt but that key has to be right. If the key has any burrs on it, they can be removed by rubbing the key back and forth on a fine file. If the key is loose in its groove, it can be tightened up by lightly dimpling its side with a center punch.

    When the flywheel is ready to go on, the crankshaft must be turned so the high point of the cam is midway between the rubbing blocks on the points. Failure to do this will result in damaging the points as the cam will be held up by the spring and the cam will catch one of the rubbing blocks. If you’re lucky, the cam will be just high enough so the rubbing blocks and oiling wick are still in contact with the side of the cam. When the flywheel and cam slide down easily, torquing the flywheel nut 40-45 ft lbs will seal the deal.


    US Member - 1 Year
    Replies: 5885
    Topics: 49

    Don’t know if this applies to the 10hp or not, but on most models, if somebody in the past has overtightened the nut with an impact wrench it will spread the flywheel taper and it will go too far down on the shaft, breaking the cam. Flywheel is ruined when this happens. Moral: Another reason to always use a torque wrench.


    US Member - 2 Years
    Replies: 498
    Topics: 63

    the OP, has the answer ” key parallel to the taper” – Wrong !
    That formed a wedge , resulting in a broken cam. Like stated above, cam should slide on with finger tip force only.

    Joe B

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