If you have a bush hog or other PTO driven impliment it wont stop right away. If there is nothing hooked up and you turn the pto on and it still spins after you disengage then there could be a problem.
Not intimately familiar with that machine model, but....
One possibility: does the PTO selector have a ground-drive position? If set there the PTO is coupled to rear wheels--ideal for use in some applications.