I've got an 86 JS300. Is the Crank seal suppose to rotate? I have the stator and flywheel off, the crank seal will rotate with the crank but if I hold a bit of pressure on it with a screw driver the seal stays stationary to the bottom end.
No. The seal should be held in place by the case. If it's been spinning in its bore for very long it might have worn the seal bore. A new seal will tell you if it is. If the new one spins but has resistance from the case you can clean the seal bore with rubbing alcohol and apply a thin coat of rtv to the seal and case before install and let it dry for 24hours after install before spinning the crank at all.