I recently purchased a 1975 Ericson 32. I noticed a blister for lack of a better term on the side of the rudder. The paint/anti-fouling around the area has cracked. You can see where rusty water was ran out of the cracks. I know very little about my boat, but I am trying to learn. What is the rudder made of and does this flaw need to be repaired before it goes back in the water? I am sure I will have more questions as I work on my boat.