removing impellor - stuck or tool required

The impeller will not simply pull out by hand or with a pliers. Is there a tool requierd or is it just that the boat I bought has not been run in a long time and it is stuck?

I have a Mastercraft Maristar 225V, 1997 with
LT-1 Corvette V8 if that makes any difference -
getting the four screws off was no issue, getting the impeller out seems impossible right now.