Doug is right and.....
I have just finished rebuilding the rudder on my '89 Hunter 33.5. I should have called Foss. $800 does not sound bad considering the hours and materials. To repair with much help and advice from the boatyard and friends, first a few (eight or ten) 3/8" holes were drilled all the way through the rudder at various locations in lower sections and watched the water drain. The boat was out of the water all winter, so the rudder had plenty time to dry. (Dryness is important.) There were many blisters which were also opened to dry. The repairs pretty much follow a traditional bilster repair job with a few added tasks. Sheathing fiberglass tape around the perimeter to prevent separation, filling the holes with epoxy resin, fairing with of Epiglass epoxy with appropriate fillers for below the waterline use added to save weight and to make sanding and shaping easier.The individual tasks involved are relatively simple, but they must be done in sequence and often require waiting for coats of epoxy or filler to dry. Since my boat is 125 miles away, I brought the rudder home to do this work a little each day. If you try this, don't forget that the rudder with the stainless steel post is heavy, hard to handle; and, you often need access to both sides at once. At noon today, I applied the last coat of 2000/2001 epoxy barrier coat as she hangs from the rafters of my garage. One more sanding and then bottom paint.... Now I read Doug's message that the foam and materials that I have been earnestly trying to preserve are inferior....Rich, there could be other problems like rust with the inner frame that could cause failure at the worst possible time, etc. Take Doug's advice and DON'T WAIT. My advice: Spend the money on a new rudder or have Foss repair and replace the inferior stuff.Good Luck, Ron