All tiller pilots of this design type use linear actuators; they are integral to the unit. Unlike below-decks linear actuators, tiller pilots, and the actuator shown in the linked article, don't have a clutch feature that provides an electrically controlled, low friction, disconnect feature. So, the tiller pilot, and the actuator shown, must be lifted off of the pin on the tiller.
I think if that actuator has a seal for the ram (I think it does), and the ram is kept greased, and the rest painted, it should be O.K.
(I have one of those linear drives, plus an electric clutch; I had toyed with the idea of making an electric, below-decks linear drive that's more rugged, and certainly less expensive, and Raymarine's. Then I came upon a Simrad electrical-over-hydraulic linear drive, cheap).