stretched cable on self propelled

I bought a used mower.troy bilt 12av839n711.i bought the correct belt and looked in the trans box and every thing works like it should but it still seems the belt isn't getting tight enough even with the adjustment all the way out.is it possible the cable stretched thru the years?it is a 2005 but it looks new and starts in one pull.if I push the mower and pull in the lever it is definetly helping but not like it should.the pulleys also look good