Hi Glsski -
I'm a Yamaha 30 owner. I'm in Vancouver. I've taken out the rudder when I had some rubbing sounds so I know the feeling when something doesn't sound right. Looks like you had some rubbing on your skeg (perhaps from a warn collar bearing but that's hard to tell from your pics. I'm not familiar with the Yamaha 26 (what year is it?) but I wouldn't be surprised if many of the parts are at least the basic system is the same.
Yours looks like the same tiller system as mine. (the wheel and quadrant option Yamaha's in the US apparently used hybrid stuffing box that is explained in the Yamaha 30 manual but I've never come across one). And a number of parts you have in photos look very similar to mine if not the same.
Most rudder systems in 80's boats are very rudimentary. Yamaha was simple but genius working with a floating rudder. Mine still floats after 43 years. And I've looked at four others in our marina and their's float too. Yamaha sailboats of the 80's era where epic for engineering and build. So well built. For the floating rudder, the idea is it would put minimal weight on the basic bearing surfaces (that top plate with the elevated crescent that is actually also a check stop for over rotation) and the bottom plastic berring as the boat bobbed up and down.
The way to test is to simply push down on the tiller shaft while the boat is in the water. It should go down about 1/4" or more and then float back up.
I wouldn't take your rudder apart just yet. I'd see if it floats first. The rudder and shaft weigh about 60lbs. Walk it into the water upright with a friend. You'll find out pretty quick if it just holds it's own as it should. If it doesn't then yes you likely have some ingress. I'd get a quote on that because that might not be cheap to put it back together. Perhaps there other ideas.
My shaft bearing was made of a type of white plastic like a cutting board. It was about 6" high - looked like a beer can without top and bottom. Very basic and held in with marine adhesive so that one day in the future it could be replaced. It hadn't been installed exactly centered. So my solution was unique and it required doing a bit of grinding in the shaft hole lip with coats of epoxy primer and I was good to go. Your bearing is worn and that's all you need to replace by the looks of it. Plastic or bronze probably doesnt matter. Find your shaft diameter Inner and outer with some spare for the adhesive and that likely would do it. Grease the shaft before you put it back - the yard probably would suggest which marine grease to use for that application.
As far as the upper bearing goes you do need to just grease them a bit. One of my neighbours had his wear out a bit and he just got a metal fab guy to build it back up.. Mine is fine.
As far as the shaft wear or scoring I doubt the yard would suggest you do much about that except clean it but get their advice - they've seen lots of these. It's not like an engine bearing or some such thing.
The advice I got from every one is that rudder shafts and their bearing are not precision stuff. That was true for my boat. Your bearing looks like it just needs to be replace with a generic collar (mine was about the size of a beer can).
Here's a link to all of the Yamaha sailboat manuals including the Yamaha 26C
Yamaha 25 Manual
sites.google.com
All thoughts above are only my experiences so take real advice from a professional in a yard. There's a guy
Let us know how you make out. If you want to chat about it on a call let me know.
Cheers!
Peter