Regarding the 'Stop'
Our '88 model, probably built by the same crew, has a piece of hardwood timber across above the quadrant. There is a solid rod of aluminum bolted to the quadrant with a rubber (piece of hose) bumper on it. This solidly limits rotation in either direction. AFAIK this was standard on all of the YS steering setups in the 80's.
There was also a cast metal assembly from YS that was part of the steering on a lot of EY boats in the 80's also.
Someone / somewhere must have removed the stop assembly from yours in the past, is my guess.
There will probably be other owners checking in, and hopefully some will even have pix to share.
For a lot of reasons the travel *has* to be limited, including the outcome you encountered. I hope that getting back to port with the emergency steering hardware was not too traumatic. :0
Regards,
Loren
ps: when you bought your boat, was this disclosed in the survey? It certainly should have been.