lube-it
I don't know of a factory recommendation but there is no ball bearing or anything like that. Just a little white-lithium grease injected through the nipple lubricates the sleeve at the rudder post. There is no other other maintenance to be done until you pull it out of the water. Then you should check for rust, wear or cracks at the post-to-rudder connection. (You must drop the rudder for that).
