Well that could very well indicate a sheared or partially sheared flywheel key. Could be other things as well, you need to do more checking. Is it getting gas, does it seem to have enough compression (exhaust valve not leaking) etc.
Engine model number is always helpful when asking for advice.

Walt Conner

Could be a stuck exhaust valve.
As Walt mentioned.....
Post the Model & Type numbers from the engine.

Try adjusting the valves, clean your carb and ensure your getting gas change the plug.

I have a Craftsman 400 DYT18.5 OHV. I was mowing my lawn and as I went up a small hill white smoke came out of the motor than it turned off. I tried to turn it on but it cranks ones or twice then it stops. I had not been mowing for no more than 5 min.

Fern-
Best to start your own new thread in the tractor section of the forum. Trying to address 2 different problems in one thread leads to much confusion-

Post the Sears 917.xxxxxxx number found under the seat.