J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Removing or Replacing Stuck Shaft

You could use a torch on the coupler to try and expand it, then a hammer. If that doesn't work, use an angle grinder to split the coupler. In any case, once all is apart, you have some cleanup to do. You may want to consider a new shaft side coupling anyway.

Another thing to try is unbolt from the transmission and slide shaft aft. Put socket smaller than shaft diameter in center, use longer fasteners on coupling and squeeze to see if it will push the shaft out.