Older boats have "straight-cut" shaft ends opposed to the newer boats with double taper, meaning your boat has a taper on the prop end, while the trans end is not tapered but round to the end. They can be a pain but here is how I do it:
1) Remove the set screw bolts, saturate with a penetrating oil.
2) Remove the 4 coupling to trans bolts & set aside
3) Slide the shaft/coupling back about an inch
4) Place an 11/16" socket (just needs to be under 1" od, usually 11/16 id works) between the trans & shaft
5) Obtain 4 trans coupling bolts that are at least an inch longer than stock & tie the coupling & trans together with the socket/spacer in place.
6) By evenly tightening the coupling bolts you will squeeze or push the shaft backwards out of the coupling.
7) After 1" of movement & it is still dragging hard, repeat with a deepwell socket until out.

If tightening the 4 coupling bolts EVENLY does not appear to budge the shaft go to step 9
9) Above proceedures fail- Cut the shaft, replace with new double taper shaft & coupling, have trans coupling refaced because it is now probably distorted.