Stufing box broke loose
Our /84 C30 had the stuffing box break loose from the fiberglass rudder tube that it is glassed into during production...one way to tell is if the stuffing box moves along with the rudder shaft or can be moved by hand..I have read this is common with these boats , however no big deal..Otherwise water may be getting past the packing within the gland inside which means tightening down the three bolts that hold it together to achieve a better seal or loosening the bolts , raise the top part up the shaft and replace the packing..If its the box itself , work it up the shaft , reglue with the best 3M you can find according to instructions and press back into place and let it set up..All of this can be done while still in the water as long as you can get things dried out..No worries mate..