In a recent 5000 mile transpacific voyage I had a RM type 1 hydraulic pump fail 100 miles after I got back to San Francisco
. The pump had driven a total of about 6000 NM, with pre event trips. The pump motor brushes
wore out, the actual pump is still quite functional. I also had along the RM tiller pilot unit that comes with the X5, the linear drive
. It packed it in after steering
for some small fraction of the 5000 miles. A stop clip on the end for the screw drive fell off and then the steering
arm came unscrewed.
My preference is similar to BOb's approach, that is independent systems in which some time is required to connect the backup.
Another approach I saw on a schumacher 52 I recently delivered, the boat had totally redundant pumps that drove a single
cylinder, which was massive. The AP designer
indicated that he has installed 100's of this setup on fishing
boats in the Washington
area and has never seen a failure. The motors and motor
drive electrionics are redundant. The computer is not backed up.
An aside on ram failures: I know of 3 local boats here that have bent their RAM drive shafts due to one abuse or another while underway. Essentially in all cases, including 1 52 footer, the wheel
or tiller was manually steered to the point of bending the RAM drive shaft.