You might have a couple options. A. You can smash it off with hammer and go out and purchase a new pulley. B. You can try a gear puller with more than two paws to gently see if it will move. C. Heat the waterpump shaft and cool it. Expansion/contraction will often break the part free, then try the puller again. If these ideas do not work, try some body else's idea or refer back to A.