T&T: auto pilots- Heavy trawler 60 tons 18 meters

[Vera Loo]

Anyone out there with experience installing a Raymarine or other brand
autopilot on a heavy full displacement  trawler with existing main engine
driven full time hydraulic steering?  Our boat is an 18 meter  2007 wooden
trawler with a single engine, prop, and rudder arrangement.  Steering is
accomplished through a wheel/orbitrol connected hydraulically directly to dual
cylinders actuating the rudder.
It  is my assumption that the course computer would be connected electrically
to a solenoid controlled directional valve inserted in the hydraulic circuit
between the present orbitrol and the plotadora valve (excuse me, Portugese
word for what i think would be a cross flow valve) directing the oil flow to
the proper cylinder according to the action of the wheel. As you can tell, I
know a lot more about the system than I understand, so any advice or input any
of the listees have would be appreciated , on or off list.
Thanks.
Robert E Barber
Trawler "MS LILIA" lying Marina da Gloria, Rio de Janeiro, Brazil