adjustable upper rudder housings

I have an older hobie without adjustable upper housings. Can I replace just the upper housings with the newer style or do I have to replace the lower housings at the same time?

You can do that.

The upper casting adjustment will allow you to get a tight fit (forward rake) into the lower casting. If you want the rake a little aft, you will have to shim the lower housing. Maybe a bit of durable selant like 3M 5200. Set the rake then squirt some sealand into the lower part of the casting where the rudder rests. Place a small mylar or saran wrap cover over the sealant and settle the rudder into it at the proper rake. Then, when the material is hard... set the upper adjustment to hold the blade there.

_________________
Matt Miller
Former - Director of Parts and Accessory Sales
Warranty and Technical Support
Hobie Cat USA
(Retired 11/7/2022)