25hp Mariner shears flywheel keys at idle

[leisjohn]

I can start the motor and it will run great until you go to idle it down to put it in gear at that point it will shear the flywheel Key. There is no back fire or spitting just shears the key. Any Ideas???

 

[Texasmark]

Re: 25hp Mariner shears flywheel keys at idle

SWAG: At idle rpm, the impulses from combustion are the farthest apart and hit the flywheel with a distinct impact whereas at the higher speeds, they are close together and result in a smoother force.

I'd say that your flywheel is loose, slot worn, incorrect key; something like that.

Mark

 

[JB]

Re: 25hp Mariner shears flywheel keys at idle

Check the stator for sticking. . . not retarding with the throttle. If it fires the plugs too soon (advanced) at low speed it may try to reverse the crankshaft rotation.

That'll shear the key every time.

 

[leisjohn]

Re: 25hp Mariner shears flywheel keys at idle

Thanks for the ideas. I will check it this week.

 

[CharlieB]

Re: 25hp Mariner shears flywheel keys at idle

While you have that flywheel off to replace the key, take a good black felt pen and completely color the shaft (taper) and the parts of the key that is exposed.

Install the flywheel, torque the nut correctly, then remove the flywheel and inspect the ink to see what contact you have with the flywheel.

It should be near perfect on the taper and NONE on the very outside of the key. Contact on the 'sides' of the key is fine, but ANY contact on the outside of the key can be an indication of the wrong key not allowing the flywheel to fully seat. A UN-seated flywheel can 'wobble' and contribute to shearing the key.