I don't think its the gearcase, prop spins easy in neutral. And engages in forward and reverse easily, but never know. Certainly could be the starter recoil. The pull handle is missing on that motor, rope could be all tangled in there.
Haven't started pulling anything apart yet, sprayed oil in the cylinders and set them aside in my living room for now. Replacing the floor and transom on the boat is my main focus right now. I'll try to get the recoil off this week to see if that makes a difference.