Difference Between Impeller and Propeller

Impeller and propeller are used to help a boat or any other waterways vehicles to move forward or backward or to help with the cooling of the machines.

Sometimes due to constant movement and the equipment parts being subjected to friction, they might get heated up. This can lead to explosions and is an occupational hazard.

Impeller vs Propeller

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 vs Propeller

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.

Comparison Table Between Impeller and Propeller

Parameters of ComparisonImpellerPropeller
Suction TypeIntrinsicExtrinsic
In Contact with WaterNoYes
MaterialRubberStainless steel
Presence Of AxisNoYes

What is Impeller?

An impeller is a system of pumps that depends on the sucking action of a rotor thereby forcing a jet of water into the boat machinery.

By machinery, it does not mean that the pump consists of nuts, bolts, and many various iron or aluminum parts, instead, the entire pump and the suction system are mainly made up of rubber-like material.

This is to help increase the momentum that is aided by the rubber to the water and also to reduce maintenance costs as iron might rust due to constant contact with water.

But that doesn’t mean there aren’t any steel or iron parts inside the pump. An axis made of stainless steel is present within the impeller and this helps in spreading the water around the entire system.

There are three different types of impellers and are called the high solidity impeller, medium solidity impeller, and low solidity impeller. Impellers are classified based on the type of fluids that it disperses or on the viscosity of the liquids that it needs to suck in.

To move the fluids or in this case, the water, the impeller adopts the rotatory motion of fluids. The energy required by the impeller to suck the water in and to disperse it around the entire system is taken from the surrounding water itself.

This helps in conserving energy and also reduces polluting the water by using other means such as oil or gasoline.

Proper maintenance of the impeller is required to ensure that there is no wear and tear in the rubber tubes and linings. Lubrication is also needed.

Even though impellers cool the engine down, it is kept far away from the engine. Impellers are kept inside a small box-like structure and the water is dispersed by other means to the engine and other parts.

What is Propeller?

Propeller is a fan that has three to four blades made of iron or similar water-resistant materials and forces water away from it. Propeller is usually placed out in the open and within the water body surrounded by water but in the underside of the boat.

The main principle behind a propeller is that it converts the rotational motion with the water is pushed away to linear motion which is the forward propulsion of the boat.

The blades are placed with even space around an axis which rotates and provides an extrinsic sucking force, that is it pushes the water away. This extrinsic force pushes the water forward following Newton’s third law.

The propeller is placed at such an angle after taking into account the size and mass of the boat that it is supposed to help move.

A propeller makes sure that the water body and the tides within it are not disturbed while the boat moves as the movement of water-assisted by the propeller is from front to back.

The propeller does not force the water to skip off to the sides of the boats and thereby does not disturb the water body. At times, with the size of the boat, exceptions can be made to the standard number of blades present in a propeller.

The greater the size, the more the blades and this would help reduce the force put on the engine to move the boat. Propellers use rotational motion and the energy needed to help in the extrinsic suction is also harnessed from the water.

It has to be maintained once in a while and searched for rust or wear and tear for proper functioning.

Main Differences Between Impeller and Propeller

  1. An impeller is placed with a box inside the boat without beginning near water whereas a propeller is placed out in the water completely submerged.
  2. The parts of a propeller are usually made of stainless steel or other similar materials whereas the parts of an impeller are usually made of rubber.
  3. An impeller work on a forward motion of the parts whereas propellers are powered by rotational motion which brings about the major difference between the two.
  4. A propeller use blades to carry out their function whereas impellers work with tubes and vanes.
  5. Impeller uses the principle behind pressure whereas propeller uses the principle of propulsion or motion.
Difference Between Impeller and Propeller


Both impeller and propeller are needed to help in the overall functioning of a boat without both movement and cooling would not be possible.

When they were first introduced, their functions seemed to be extreme opposites and at that time there were many differences between the two.

But as time passed, with the introduction of the latest technology, both the functions could now be carried out with a single part or device attached to the boat.

Bernoulli’s principle is a major driving force for both impellers and propellers as it deals with the motion of fluids. Back in the day, propellers were not known to create a backward motion, but now it can be achieved with propellers.


  1. https://asmedigitalcollection.asme.org/gasturbinespower/article-abstract/103/4/688/405065
  2. https://www.sciencedirect.com/science/article/pii/000712269190179N
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