What part of rotates to power the boat forward backward?

In a boat, the part that rotates to power it forward or backward is typically the propeller. When the engine turns the propeller, its blades create thrust by pushing water backwards, propelling the boat forward. By reversing the rotation of the propeller, the thrust direction changes, allowing the boat to move backward. In some cases, boats may also use water jets or outboard motors to achieve similar propulsion.