Just happened to come across this thread. I have a 1980 Cherubini Hunter 36. Same YS steering system.
Just a thought here. When you have the compass off, try to inspect the control head piece.
Merriman / Yacht Specialties Pedestal Control Head.
If yours is still original and made of plastic like mine is, the plastic is likely to be now quite brittle. The "bolt-to" connection points for the fuel and shift legs (as shown on page 12 of the pdf that kloudie1 referenced in his earlier post), have been known suddenly to fail making it impossible to shift from forward to reverse for example.
I discovered my control head was stress cracked back in 2007 when I had the pedestal off to repair the cockpit sole. I don't know if its possible inspect without taking off the head, but maybe twist things around a bit with some needle-nose pliers and look for stress cracks opening up. Or shift between forward and reverse while looking into it. Torquing the throttle and shift handles off center left/right also might reveal a potential failure point. Maybe a small dentist type mirror might help?
If you do want to replace the head, be prepared for the SS bolts screws to be very difficult to remove! The galvanic corrosion of Stainless Steel vs Aluminum issue.