flywheel key keeps breaking

[erniej]

motor keeps shearing flywhell key on my 1979 evinrude 70 hp motor. this is operating under normal conditions. thanks for any help.

 

[norman158]

Re: flywheel key keeps breaking

you must torque the nut on top down to your manufacters spec. take a little sand paper and scuff up the taper on the crank and inside the flywheel before you reassemble

 

[Joe Reeves]

Re: flywheel key keeps breaking

Ernie.... If the flywheel key shears, even once, damage will occur to the flywheel and crankshaft taper. You'll need to restore the tapers before re-installing the flywheel and nut.<br /><br />The nut must absolutely be torqued to 105 foot pounds. Anything less, even if the tapers are perfect, will result in shearing the key again.

 

[P.V.]

Re: flywheel key keeps breaking

Well, I would believe there are a couple of reasons why it keeps hapening. 1st. You are not assembling it correctly. Oil on the taper of the crank or the flywheel. A "mis-matched" taper will not allow full contact between the two. Clean the tapers and then use a very small amount of valve lapping compound, turn the flywheel a few times to "seat" the two. Clean very good. Clean again. Torque nut to specs. 2nd, you have a mechanical "bind" in the powerhead or in the gearcase. Could be a bearing , piston, gear tooth. Turn the engine over by hand with the plugs out. Should turn with no "high spots" . no binding up. If you find something, remove the gearcase and see if the problem goes away. ?????? Also see if anything like the timer base or stator under the flywheel is contributing to the problem. Good luck !!! P.S. If you clean the tapers and the problem still is there later, you must have a mechanical problem. Keys shear usually only once. Not two or three times.....