mechanical linear drive that Autohelm (now Raymarine) sells. I have steered over 125,000 miles on two of these and they are both still good. They have worn out brushes and I have had to replace the plastic gears but that is all the maintenance they ever got. The circulating ball drive is almost indestructible. I'll bet Autohelm did not design or build them. The design is too good compared to some of the other crap they sell.

As I said in my post, most hydraulic autopilots seem to leak sooner of later. I hear the same story over and over again in remote destinations: "Bilge full of hydraulic oil and our spare oil used up".

The problem you describe is obviously a different one. Could it have been undersized for your 50 footer?