I bought a 1975 Bystedt 30 one year ago. The boat is powered by a Yanmar 2GM (the old model, older than 2GM20). The engine is connected to a Cessna hydraulic pump. It took me a long time to find the stamped model in the flange, 5H 12 PA - 70142 RAG, which according to http://knighthawksupply.com/cessnapumpid.htm means Product type 701, Pump configuration Tandem, Displacement 0.84 in 3/r and Right-Hand rotation. All this is located below the cockpit. Hydraulic liquid is pumped there to the hydraulic motor in the bilge, with a load adaptor that connects with the shaft.
The hydraulic motor and the adaptor were totally rusted, the shaft almost loose. I found a clue of what happened to the boat in a blog of the previous owner. He was 20 miles southwest of Cape Flattery, when the bilge start filling up with hydraulic liquid, and the shaft stopped spinning. He adds that the previous owner told him "It's a closed hydraulic system - both ends are identical.".
I asked for advise in a boatyard nearby, and they told me they could fix it for $12,000. That's more than I paid for the boat, so I decided to work on it myself. Dave, a local boat mechanic lend me a hand, and we removed the old unit:
We found out that the problem was the adaptor, so we found a replacement (that was about $1,200). The replacement didn't match the exact size of the previous unit, so we had to make some adjustments on the metal sheet that served as a base. After all this, Dave installed the new one and repainted the whole thing:
It works like a charm now. The whole thing took us a couple of months, but in Seattle the weather encourage us to work inside the cabin.