[C320-list] autopilot

[Koen Bennebroek]

I'm considering adding an autopilot to Big Cat. Most Catalina's I've  
seen use the ST4000 or the MKII. It seems that both have been  
discontinued and replaced by the S1.
Apart from the rudder transducer, is there a difference between the  
models? Is there a reason to choose the S1 over the older models?
Also, how hard is the install? I assume all of this can be done while  
the boat is in the water?

Thanks, Koen
(Big Cat, 1995, #224)