Boat hasnt moved in a few years. I got motors running and find shift shaft siezed. Is there any way to free it up?

Take the shift spool out and inspect it, take the lever off, then the triangle plate the neutral switch threads into and slide the whole valve assembly out

Bfh!

is this doable with trans still in place?

Yes, it is.
Once you remove the lever, the detent ball & spring is behind, so be prepared to catch the ball while removing the lever.
Behind the 3) bolt plate w/ NS switch is the detent plate for the switch.
If the Shift Spool is bound, you can use a socket that will fit over the threaded stud for the lever,,,,you don't want to hit or press on the threaded stud part of the spool.
You will need a new o-ring for the lever side, and new gasket for the plate side. Clean the bore out on the lever side, without getting debris in trans, grease only going back together.

Dereknkathy- your mailbox is full. Tried to reply.....

Got it freed up. Hi cetane's info was on the money. 3 bolts on cover plate orig 7/16 bolt head. ended up driving 10 and then 9 mil sockets on and they unscrewed easily. Bang shaft out with 5/8 deep socket. Reinstall and drive away.