They used to be called screws, but I'm not sure if that was just a British idiom, or an obsolete phrase.
They may also be referred to as a "wheel".
boat propellers
The Florida manatee is often injured by boat propellers, as they often bask just below the surface, and cannot be seen by boaters.
Another name for a tippy boat is, CANOE
The another name for canal boat is BARGE
it will hit them and hurt them seriously
The Amphicar. Built in the 60's. Not a very good car or a very good boat but it had propellers and could be driven slowly into the water.
He was killed in a boating incident. The propellers of the boat cut him.
The oars or when a motor is used, the propellers on the shaft sticking in the water.
Power Boats, Yachts. Any boat that has a motor on it. Or one that is powered by human and has a propeller on it (mostly known as a pedal boat or paddle boat).
Rotors, they are generally so-called (Props) applies to conventional propellers on conventonal aircraft, of course an autogyro or a Rotordyne has both propellers and Rotors but that is a special case.
what is the name of the pleasure boat that collided in the river themes?
The majority of boat props are aluminum. You can't solder it, it has to be welded or heli arced.