I disconnected the two wires on the motor
of the Cetec Benmar power unit and wired the output of the AC42 directly to these terminals. All power was disconnected from the power unit so the only power for the motor came from the AC42.
I did the dockside commissioning of the auto pilot and all seemed to work fine. It will be a while before I can do any sea trial.
So to answer your original question, yes, it appears you can save some money
and use you original pump.
The install of all the components, (AC42 autopilot computer, RF24 rudder
position sensor and Airmar H2183 heading sensor) were very straight forward and didn't take a lot of time. Easily done in a day if you already have a NMEA2000 network to tap into and all the cables
and wire on hand.