I have an older(1977) Hobie 18. Well, at least the rudder system, which is just about all that is left of the original boat is 1977. I got a great deal on a set of EPO rudders to replace the reeally bendy black plastic ones that I have.
The problem is, they don't fit! The castings, both upper and lower, have these molded-in bushings that limit the space for the head of the rudders. I sanded the ruders, but I am getting to the glass and can't go any thinner, so I am left with having to modify the castings. Any ideas other than grinding the heck out them? And what should I use to do the grinding?

I don't know what the answer is, but you might try posting on the Hobie Forum: www.hobiecat.com/community/index.php , and the Beachcats Yahoo forum/list. You can find the link at www.thebeachcats.com . Good luck!

When I had my 82 18 mine were too wide for the castings as well. I sanded them down alot and bent the rudder casting out a just tiny bit. They eventually fit, it was tight but they fit and the tight fit eliminated all slop.
Good luck, just keep sanding away.
-Todd

I had the same set up and problems. I sanded the hell out of the blade tops and used a angle grinder on the casting cleaning that up with a flat file. Keep at it.