1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need help!!

[jpmobydick]

Working on 40 hp 1969 Evninrude Model #40952R with friend. Starts easy runs for up to five minutes and then shears woodrift key between flywheel and crank. No engagement of gears or anything. Nothing is siezed anyways. No sound of sudden loading that might cause this or give us a clue. Happened 5 times. Same way. We are at a loss. Just wondering if anyone out there has run into this. Any help or suggestions would be much appreciated.

 

[fireman57]

Re: 1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need he

Sounds like you are not getting it torqued to spec. I don't remember offhand how many foot pounds it is, I believe it is 40-45lbs, but a quick search would find it for you. The only other way is that your slot is wallowed out resulting in a little bit of slop which is all it takes.

 

[jaykibo]

Re: 1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need he

Im not sure about your motor, but I have a 50hp Mariner that uses the woodruff key on the flywheel only to make sure the flywheel it put on in the correct position. The actual taper of the crank is what keeps the flywheel in place. Any torque transferred to the flywheel is through the tapered crank and not through the key, otherwise it would shear the key.
If yours is the same then I would suggest you make sure you bolted down the flywheel properly with the main (middle) nut and its 'biting' down on the taper properly.
My woodruff key was so worn I had to throw it in the bin and make a new one out of a needle bearing I had lying around, it was loose but it did the job as it was only used to guide the flywheel. Once in place the taper does the rest.

Hope that helps.

 

[lindy46]

Re: 1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need he

The flywheels on the 40hp have to be torqued to 100-105ft.lbs. If you're not torquing them enough, you'll shear the key.

 

[fireman57]

Re: 1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need he

lindy thanks for the proper torque. I figured I was wrong going from memory.

 

[F_R]

Re: 1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need he

Bottom line and the truth is, the tapers must be clean and dry, and you must use a torque wrench to tighten the nut to 100-105 ft/lbs. If you do not heed these instructions, it will shear the key. When it shears the key, it damages the keyway and tapers. And the next time, it causes more damage, and the next...you get the idea.. So, you have repeated it a number of times. It might be beyond saving. It must be in perfect conditon. Take a real critical look.

 

[jpmobydick]

Re: 1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need he

I have taken note of all the advice and will apply it the best I can. I hope with success, will let you know how it all turns out. Once again thankyou to all.

 

[wilde1j]

Re: 1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need he

If this has happened more than a few trimes, the crank and flywheel may be junk.

 

[Joe Reeves]

Re: 1969 Evinrude 40hp Problem with shearing Key between Flywheel and Crank. Need he

NOTE: Do not attempt to use some woodruff key purchased from some hardware store, use only the designed key which is available at your dealership..... part number 307480.