I have an old McDonald centrifugal pump used to pump lake water to our garden. It was working great but it now seems to 'bind'; sounds & feels like the impeller is rubbing.
I have tried to take it apart to examine the impeller but with no success. I removed the 4 bolts that hold the 2 halves together and the motor section is loose and will rotate about 1/4 of the turn either direction, but I can not separate the halves. There appears to be another plate under motor mount with another 4 bolts. These bolts are partially visible through slots in the mount, but are not accessible.
Can anyone tell me what needs to done to open it?

A.Y. McDonald MI-T-FLO
Model number 4432