Troy Built mower mdl.#14av809h063, cannot get drive belt off engine pulley,frame tabs prevent removing belt. How do you replace belt?

Well you can remove the center bolt that holds on the pulley and allow the pulley to slip down a little, or you can take a large, long punch and a hammer and carefully tap on the tab to get the clearance needed, you only have to do this on one side, not all three tabs, then work the belt off, then put the new belt on. Then bend the belt guard back into place. If the pulley will slip down a little, that is best.