I will just add to this.
I have had both systems , my last boat was 48 feet and had a linear hydraulic drive , it worked just fine, the only concern I have with them is the way they are installed . The end of the ram takes the full load of the rudder , if you are getting into some nasty weather
the point were that ram is attached has to be enormously strong ! This was not a problem on my last boat it was aluminum
, I can see issues if you are doing laminations to the inside of the hull
. This has to be very strong!!! I have seen many rip right off the hull
and take everything they are attached to go with them, IE bulkheads and stringers .
My present boat has a below deck
Mamba drive , which turns via a chain a rack and pinion gear set up that is attached directly to bottom of the rudder post , This is completely separate from the cable system that I steer with . The solid bronze gears take all the rudder load , the Mamba drive sees no load at all , the mounting of the drive is not crucial other then the alignment of the chain .
Of the two which one do I prefer ? They both work great but to tell you the truth I look at my rotary drive much less then I looked at the linear drive . The stresses on that ram always gave me concern .
I like the rotary drive for its simplicity . Just the electric
to worry about , not the electric
over the hydraulic . One less system to break or maintain .
Also the Mamba drive is whisper quiet . If it makes a noise it is usually just in need of a chain lube .