The fluid does bypass when not being called on to push in one
direction or another so I'd venture to guess it could just be tight.
All my boat ps experiences are that they turn pretty effortlessly.
Did you not have ps on your prior boat?

I do have an 200hp outboard boat with hydraulic steering. There is
more resistance.

It's been about nine years since I had an I/O with power steering,
although I have driven others as recently as last September. Last one
I drove had exactly the same motor and outdrive as this new boat. I
don't recall it feeling this "over-boosted."