had the shop put a new water pump in, drove 3 hours to the lake started out got out about a half mile and noticed the temp was was up, slowed down and the temp started comeing down looked like it was pumping a good stream, got home pulled lower unit and top of water pump there is very little of the impeller left, the problem is somehow it has cut a grove in the shaft and i cant get the impeller off, now im afraid that grove is going to leave a weak spot in the shaft, any ideas