Hi,
I have a princess33 mk11 (1984) with Hynautic steering system,
which consists of 2 helm units a reservalve (rv55 I think,) and a
single ended cylinder driving the twin outdrives. I,m hoping to fit
an autopilot to the system ,can anybody give some advice on which type of autopilot I reqire , and which components i require.

Cheers Paul.

It sounds like you need a hydraulic pump autopilot system so your existing steering system will need to be plumbed into.