tug
Boat propelled by powerful engines that is used to tow boats and other floating craft to help them maneuver or to rescue them.
propeller 
Device with blades integrated onto a shaft that is driven by the engine to provide thrust and thus impel the ship.
rudder blade 
Part of the rudder that receives the thrust from the propeller in order to steer the boat.
wheelhouse 
Cabin that houses the pilot and the navigation instruments.