The main difference between impeller and propeller is that the impeller is a part of the overall machinery in a boat that acts as a cooler thereby ensuring that no accidents happen by overheating of the system in the boat. On the other hand, a propeller is a part of the boat that helps in the forward or backward movement or propulsion of the boat.
Impeller pumps in the water from the surrounding ocean, sea, or whichever water body the boat is moving in to cool the machines present within the boat which might be overheated due to constant use and the action of friction that might make it susceptible to burning away of rubber or plastic parts or even an explosion.
A propeller is a fan that helps in the motion of the boat in a forward or backward direction depending on the model and year of manufacture of the propeller. The fan moves in a certain way and forces the water to move between its blades, therefore, creating a pressure movement in the boat. It is the main reason a boat moves if not rowed.
