We hope deep inside the rudder everything is okay. We drilled a few holes here and there to try to see where the water can go. The rudder is built like the boat, with two halves seamed together. Down the center are two sheets of plywood surrounded by a stainless frame. The rudder is filled with all kinds of material for filler, i.e. left over mat, glass cloth pieces and probably even floor sweepings from the glass shop. 

Two things, first the frame bends around the prop opening making it almost impossible for the shaft to spin free in the rudder.  Second the filler material helps to keep the stainless frame from being immersed in water. But obviously it can happen.