There's two different types of propulsor, depending on the fixed and moving blades configuration. I can't remember the pros and cons of each type now though. I only ever had one boat fitted with a propeller, not counting the one big grey thing I had.Lot of technology in a boats propulsor! First time I saw one I thought - now that is a propeller!!!!
You'd laugh if I told you how Westlands put a 1.5 degree twist on a rotor blade!!!!
The rotor blade is placed in a jig. Then a geezer holding a huge length of scaffolding pole hangs off it until the angle is reached!! Seriously hi-end tech!!!!! I would like to think the blades that keep the Merlins and Wildcats airborne are built using a bit more tech!!