My son hit a branch with our Zero Turn. Said it sounded funny and shut it down. I put the belt back on, but it keeps throwing it. Before it throws the belt, the mower runs, but it seems to be running at half power. The blades are undamaged and spin level and free. The belt seems to be in good condition as the mower is less than a year old. I adjusted the tension on the belt, but it only resulted in holding the belt a little longer. There is some bounce in the belt when its running. I'm not sure how smooth it should be since I have never seen it run with the cover off before. The tensioner seems to be working and the pulleys don't look damaged. 54" Zero Turn Husquavrna with a 23 HP Kawasaki 4 stroke v-twin.