@chuckypoo, Charles, If your sears mower was equipped with the Briggs and Stratton eng., may have a failed head gasket as it seem's to be a often occurrence. If mower is still in good condition it would be well worth having diagnosed, especially if it was only needing head gasket or even simpler repair.
Blue or white smoke coming from your engine usually indicates burning oil, which can be caused by:
-Overfilling the crankcase with oil
-Incorrect oil grades
-Operating engine at greater than a 15 degree angle
-Inoperative crankcase breather
-Crankcase air leak
-Blown head gasket
-Worn cylinder and/or rings
Links below may help trouble shooting and repair of head gasket. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.