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Impeller vs Propeller: What’s the Difference?

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Impeller and propeller,they may sound similar, but their purpose and function could not be more different. For example, both are used to operate boats but are functionally diametrically opposed. A propeller is a fan that pushes a fluid by pushing it, converting rotational forces into linear motion. An impeller is a rotor, usually part of a pump, that creates suction, which draws fluid into a vehicle or engine. Let’s take a closer look at what these components are and what they do.

3D file water jet impeller
3D file water jet impeller


Simply put, an impeller is a rotor that produces inherent suction as part of the pump assembly. In the case of a boat, the impeller is made up of a series of flexible rubber blades attached to a central hub. The hub rotates around a shaft in a stainless steel liner inside the pump. Cold water is pumped through the impeller to the ship’s engine to cool it under load. A pump in a Marine engine has an impeller that draws water from outside the ship into the piping system.

There is an inlet on the impeller that provides a channel for water inside the boat, and rubber blades push fluid through the inlet. The impeller is the rotating part of the centrifugal pump, which pushes the fluid away from the center of rotation. As a result, energy is transferred from the pump to the water, which creates velocity in the water, making it move outward from the pressurized pump. The Archimedes screw can be seen as a very early and basic version of the impeller.

High, medium and low solid degree impeller

Impellers can be divided into three different categories: “high,” “medium,” and “low” solid types.The special design and size of these blades prevent gas from flowing around them, which would be more likely if the blades were narrower in shape.

  • High solids impellers have fairly large square blades and are used primarily for dispersing gases and mixing fluids of high or moderate viscosity.


  • The blades of low solids impellers are much thinner than those of high solids impellers. They are commonly used to mix low viscosity fluids and solid suspensions.


  • The blades of low solids impellers are much thinner than those of high solids impellers. They are commonly used to mix low viscosity fluids and solid suspensions.


  • Medium solid impeller is an intermediate strip between high and low, naturally.


A propeller is a fan that pushes fluid away from it, converting rotational motion into linear motion (external motion). Similarly, in the case of a boat, the propeller acts like a fan to generate thrust, thus powering the boat’s movement. Typically, propellers consist of three or four blades that rotate around an axis to produce forward motion. As the blades rotate, the water pressure behind them increases, moving the boat through the water.

This is possible because the blades protrude at an Angle from the hub, allowing the water to go from the front strut to the back without pushing the water to the side. Generally speaking, the more blades on a propeller, the more power it can generate for the aircraft. Increasing the number of blades can also reduce the amount of drag that occurs. The thrust produced by propellers can be explained by Bernoulli’s theorem or Newton’s laws of motion.

Ducted propellor design model
Ducted propellor design model

What are the main similarities between an impeller and a propeller?

Impeller and propeller have many similarities:

1. They all use rotational energy to move fluids in some way.They’re all driven by an external motor.

2. Both require ongoing maintenance to keep them operating at peak performance.

3. Impellers and propellers use water to generate energy for both propulsion and pressure.

4. Both require regular lubrication to prevent their parts from wearing out in a short time.

Going back to our boat example, they are both crucial to the operation of the boat, without the propeller, the boat cannot move, without the impeller, the boat cannot maintain the temperature of the engine.

What is the main difference between impeller and propeller?

The main difference between the two is purpose and function.

  • Impellers are usually the main part of the cooling system, and they must draw water into the engine while it is running to keep it cool and at the right temperature.
  • Propeller is the main component of vehicle propulsion system. They create motion in vehicles such as boats and planes. The faster the propeller blades turn, the more speed and acceleration they produce.


Even with this major difference between the two, there are still other minor differences between the two components:

1. The impeller is included in the pump housing, but the propeller is not.
2. The impeller uses the blade to suck the liquid, and the propeller uses the blade to push the liquid away.
3. The impeller moves forward and the propeller rotates clockwise.
4. The impeller produces pressure, while the propeller produces water propulsion.

impeller vs propeller
impeller vs propeller

The main difference between an impeller and a propeller lies in their design, function, and the applications in which they are used.

DesignA rotor-like device that consists of blades or vanes that revolve inside a casing or housing.A fan-like device consisting of two or more twisted blades.
FunctionIncrease the pressure or flow of a fluid.Uses the blade to suck the liquid.Pushing a fluid (such as air or water) to create thrust.
Motion DirectionImpellers move fluid by pressurizing or drawing it.Propelling vehicles forward or backward through a fluid medium.
ApplicationsPumps (centrifugal pumps, axial flow pumps), mixers, agitators, and certain types of turbines.Marine vessels (boats, ships, submarines) for propulsion through water and in aircraft for propulsion through the air.

Type of impeller

Propellers can be fixed pitch, controlled pitch, reverse rotation and water jet propeller.

1. Fixed Pitch propellers — These are the most common propellers you’ll see on recreational boats. It is a powerful propeller, but cannot be adjusted or matched for performance according to operating conditions.

2. Controlled Pitch propellers – As the name suggests, this type of propeller allows the captain to make adjustments and adjustments as the boat moves. Such propellers are more expensive to buy and maintain.

3. Counter-rotating propellers — These are twin propellers mounted on a single shaft. Each propeller spins in the opposite direction. These types offer excellent maneuverability, but are not very rugged.

4. Water Jet Thrusters — Water jet thrusters have no propellers and can drive small boats or ships. It works by pumping liquid through a tube that serves as a propeller. These are usually found on motorboats and speedboats.


There is a comparison between impeller and propeller. The impeller and the propeller are two different parts of the engine. The impeller is part of the engine pump of the ship’s engine system and helps to avoid overheating.

The propeller is the part that pushes the water to make the boat go forward. Both components perform a rotational motion to operate.

For More Information

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