Hmmm,
I've been aware of only one boat with Hydraulic steering and it was at that time on the Western Shore of the bay. It was being offered for sale by a broker, with a photo and a very lengthy description of modifications that had been done. At that time, it claimed a 15 or 16 HP Yanmar.
When I contacted the broker, he sail that he was removing it from his listings because the owner wasn't cooperative and had not been taking care of the boat for showing. I was never able to identify the hull number or actual location.
I do have the listing in the bottom of a box somewhere and will be happy to mail it to you when found.
sfisher896@aol.com