Twice now when turning off the mower deck my belt has slipped off the pulley. I checked the pulleys and they all seem tight (no loose bearings) so does that mean the belt is probably stretched out and in need of replacing? Also, I can hear the blades lose power if I raise the deck with them still engaged.
Yes, I would start by replacing the belt. Before I put the new one on, I would pull the idler pulley and spin it in my hand. If you feel any jumping or bearing growl, I would also replace it.
