Thank sail sfbay for your suggested reading! I decided to just pull it and see what I found...
For those interested in this topic I thought it might be good to post the solution.
There are various rudder models of the Yamaha 30. Mine was the Canadian tiller model. The description in the Yahama 30 original manual is for a US wheel model (not the rudder model). Because the wheel model requires a quadrant, the shaft appears to be exposed on the inside of the haul relatively close to the hull floor, and nearer the waterline. The schematic shows a stuffing box to keep the water out. Makes sense.
On the Canadian tiller model, its a much simpler and elegant solution. There is a fibreglass shaft tube glassed from the rudder hole under the stern up and inside of the hull that extends up to within 2 inches of the top of the exterior deck - where the tiller attaches. The tube runs so high that seawater can never reach the top. - so its doesn't need a stuffing box. The rudder's shaft installs up through the hole and shaft tube to the top where it is held by a cube shaped clamp that compresses with one bolt. This bolt threads through both the tiller as an attachment and the clamp and together they are compressed by a nut. This all grips to the shaft and it's affixed. Some people might be concerned if, while in the water, they remove the nut to remove the tiller, say to varnish it, the rudder would drop out. They would be right... except that the rudder itself floats and is thus suspended in it's elevated position while in the water. BUT many rudders of various brands of vessels eventually leak with age and fill with water - and don't float. I was shocked to see that this one still floats after 40 years of service. Well done Yamaha!
You can test this while in the water by simply pushing the tiller shaft down about a half inch and watch it float back up. If it doesnt float the clamp is probably resting hard on the stainless steel deck flange, and likely has signs of rubbing and wear on the clamp. No matter, it's probably still working well enough for you. But you want to be sure it still floats if you're removing the tiller while in the water.
Whether it floats or not, if you're out of the water and you remove the bolt it will drop! You need people below to support it.
The upper deck hardware is in fact the rudder shaft upper bearing. You should probably apply marine grease it if you don't see any. Yes it's primitive but most tillers bearings are as I've discovered. This one is good.
The lower bearing, in the tube style rudder, is collar style that rests about 2 inches above the entry hole you would install the rudder. It looks like a can of beer with the top and bottom taken off. It's made of a type of white hard plastic designed for this, is 90mm long and accommodates a shaft 60mm in diameter. When I looked at mine it was in good shape. And a tech confirmed the rudder was straight. Good stuff. I cleaned the shaft with kerosene to clean off all the crud. And re-greased the shaft and bearing with an advanced marine grease provided by the yard. It all went back in with a gentle shimmy and we bolted it back up.
The shaft is really long. You can't drop it enough to remove the rudder while resting on the hard. You will need to get the yard on haul-out to raise it with the keel about 3 feet or so above the hard and you release the rudder from the top and drop it with some people below. They may have to lift it slightly to take the pressure off the top of the clamp. It's not heavy... maybe 60-80lbs so two people below is plenty. You then have to wiggle it out. And of course on the launch they need to raise it above it's resting height on the hard to get the rudder back in. Bolt it up, and then off you go to the launch!
This is not a hard job. It's pretty straight forward. It needs good relations and coordination with the yard and you're good to go. For those doing a quick re-grease or inspection you can probably get away with just dropping the rudder a few feet while on the hard and greasing the shaft surface. In my opinion, I wouldn't panick if you see minor scoring on the shaft where it meets the bearing surface. Marine stuff can get in there although those two donuts between the rudder and the hull do help to prevent that. It's not an engine bearing of fine precision. If you hear noise while at sea or on the hard as you rotate it that would be a different matter. In my case I was happy I did the removal as someone had dropped a small screw and washer into the shaft... and that came out with the rudder.
My yard didn't charge me for this extra fiddling about.
Overall I'm very impressed with the build of this rudder and shaft. The shaft is beefy, and typical of Yamaha it's overbuilt and ingenious.
The result... well it's smooth as butter. Should be good for another 40 years.
All the best!
Peter
