The V-belt is turning over in the motor pulley. The Primary Mower V-belt is not sitting the right way in the V on the motor pulley which is chewing the belt up.The belt is OK in the other pulleys. If I have the tension to tight the motor will not start because it turns the blades on the mower when the mower is still not engaged. I would like to know what I have to do to fix this problem because the new belts are not lasting very long!!

What model do you have? You can not start any Sears tractors with the blade engaged, there is a safety lockout switch. Belt diagrams are most frequently on the mower deck.