Evinrude Kept Breaking Flywheel Keys

[Kiggsia]

I had a 40 hp Evinrude, uncertain of year probably 1960's, that would start, idle, run slow fine. But when I tried to accelerate, the key securing the flywheel to the crankshaft would shear every time. Of course I made sure it was timed right, all ignition components seemed ok, and I don't think it would have started and idled so good if points, plugs, condenser, coils were bad. After several breakages and attempts to troubleshoot, the flywheel was so tight I could no longer remove it with my flywheel puller. I traded it in on a new Johnson, and later asked the dealer if he got the old Evinrude running, and he said it did, that it needed new points. But I wondered if he ever gave it a high speed test in addition to the test tank test. Might anyone have any input on such a motor problem?

 

[lindy46]

Re: Evinrude Kept Breaking Fywheel Keys

Re: Evinrude Kept Breaking Fywheel Keys

Did you use a torque wrench? Torquing too little or too much will result in a sheared key.

 

[tashasdaddy]

Re: Evinrude Kept Breaking Fywheel Keys

Re: Evinrude Kept Breaking Fywheel Keys

agree 100% not properly torqued.

 

[F_R]

Re: Evinrude Kept Breaking Fywheel Keys

Re: Evinrude Kept Breaking Fywheel Keys

agree 100% not properly torqued.

Yes, it all comes down to the basics and a few Must-do's. You Must be certain that the tapers are clean and dry. Then you absolutely Must use a torque wrench to tighten the nut to 100-105 ft/lbs if it is a 1-1/16" hex nut or 60-65 ft/lbs if it is the older 7/8" hex nut.

If the Musts are not followed, it will shear the key and damage the shaft and flywheel. Do it again and it will cause more damage. Every time it shears it will get worse, until it is impossible to ever again get it to hold. Two times is usually the limit.

 

[Kiggsia]

Re: Evinrude Kept Breaking Fywheel Keys

Re: Evinrude Kept Breaking Fywheel Keys

No, I didn't use torque wrench. Used the "Gudenteit" method. I can see how a loose nut would cause key to shear, causing the flywheel to raise up on the key enough to shear it, as the key isn't in there very deep. But how does overtorquing cause anything other than binding and seizing?

 

[wilde1j]

Re: Evinrude Kept Breaking Flywheel Keys

Just torque to the correct value for your motor and if the tapers are not already damaged, it will hold fine. Too much, and things can bind and/or break.

 

[Joe Reeves]

Re: Evinrude Kept Breaking Flywheel Keys

If you think you're over torquing simply by tightening that flywheel nut as tight as possible, you're mistaken. If over torqued, the danger of having the flywheel taper spread exists BUT that will not cause the key to shear.

The key must be installed with the straight edge perfectly vertical with the engine's driveshaft, crankshaft, etc, NOT aligned with the crankshaft taper, and the flywheel torque must absolutely be 105 foot pounds. Ignoring these two area results in a sheared key.

Also..... after once shearing a key, the crankshaft and flywheel tapers must be cleaned up, get rid of the burrs, etc. If the flywheel can't set properly on the crankshaft taper, torquing can be a waste of time.

To torque, one needs the proper torque wrench and socket, and also a flywheel turning spanner wrench so as to hold onto the teeth of the flywheel.

 

[Kiggsia]

Re: Evinrude Kept Breaking Flywheel Keys

Thanks Joe Reeves, this has been the most helpful amount of info about this problem.