Guys, Guys ,Guys. Remove the backplate, cylinder and piston. Put one of those black 6X32 cap screws in the front end. Place the crank case on a wood board andtap on the screw head with a hammer,(gently).
If you use the wrench method on the retaining collar (to remove the prop drive), the wrench will gouge the collar badly and make a mess. It will also crush the phenolic thrust washer in between.