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Impeller vs Propeller: What Are the Major Differences?

Written by J. Harvey / Fact checked by S. Numbers

impeller vs propeller

The impeller and propeller are critical parts of your boat or the engine system. This impeller vs propeller comparison discusses their purpose, how they work, and their major difference.

An impeller is part of the centrifugal pump of the boat engine that sucks sea or lake water into the pump housing and circulates it for cooling. On the other hand, a propeller is a component that propels fluid or pushes water to move the boat in a particular direction.

Propeller vs Impeller 

The impeller and propeller are important components of a boat’s engine system. A Propeller vs impeller comparison is important for boaters to understand how they function. This comparison will provide relevant information to the boat owners on maintaining these components.

Impeller Propeller
Component of a cooling system Component of a propulsion system
Uses vanes Uses blades
Intrinsic suction Extrinsic suction

What is an Impeller on a Boat? How Does Impeller Work?

agitator-and-an-impeller

An impeller is part of the engine that keeps the engine cool. It is a part of the engine pump that moves in a rotational motion and sucks water into the boat’s machinery. 

Impellers use rubber vanes molded around a hub. The hub moves in a rotational motion in the pump housing to draw fluid.

Impellers are responsible for transferring the energy from the pump’s motor to the water. This process creates the pressure inside the pump allowing the distribution of the fluid to keep the engine cool.

To simplify impeller meaning, it is a rotor that moves in a forward motion to produce a sucking force. The suction system of an impeller is intrinsic. An impeller is powered by an impeller boat motor.

Basic impeller proper maintenance include, constant lubrication, regular gasket replacement, and using the proper tool (impeller puller).

Types of Impeller

There are 3 main types of impellers: open, semi-closed, and shrouded.

  • Open Impeller – Because an open impeller lacks a wall, it is easy to maintain. This impeller is commonly found on smaller pumps.
  • Semi-closed Impeller – This impeller is partially covered, as the name implies. This impeller can be stronger than the previous one, but it is less efficient. This impeller can actually handle mixed solid-liquid mixes.
  • Shrouded Impeller – This impeller has walls on both the front and back sides, making it more durable. This impeller is often seen on big pumps, although it is not suitable for usage with solids-containing mixes. They are also more expensive and more difficult to maintain than the other sorts.

Impeller Vs Other Engine Components

Impeller vs Rotor

You learned that an impeller is a rotor. Does that fact make them similar? As the impeller is part of the engine pump, it is also called the “impeller pump.”

In terms of behavior, they are the same. In other words, you can consider an impeller as the type of rotor inside the pump.

You can define a rotor as the rotating part of a pump. Other pumps, like a seal and a shaft, may have a rotor but do not have an impeller.

Impeller vs Expeller

Like the impeller, expeller is also part of the pump. It is a disc positioned behind the impeller. The expeller rotates in the pump’s shaft to help seal the liquid.

Agitator vs Impeller

Agitators often relate to washing machines. You probably also heard about impellers on washers. Then you wonder, are they the same?

An agitator and an impeller are technically not the same. An agitator is a device that has a shaft and an impeller. Its main purpose is to import motion in the form of stirring.

Does Turbine Engine Use Impellers?

A turbine engine or what others call an impeller engine, is a machine or a device that converts the rotation force from a fluid into a consumable energy.

Turbine engine or turbine pumps and the typical centrifugal pumps feature different designs of an impeller. Turbine impeller is smaller in diameter and features multiple small vanes.

How to Maintain an Impeller?

  • To keep the impeller from drying out, keep it lubricated. It is suggested that a special lubricant or dishwashing soap be used.
  • If the gasket becomes brittle, replace it immediately. Frequent checking will alert you when a replacement is required.
  • Pack a spare impeller in case you need to replace the broken one. Boat moves owing to impellers and propellers.

What is a Propeller on a Boat? Propeller Meaning

what-is-an-impeller-on-a-boat

A propeller moves the vessel by propelling water with its fans with blades. Typically, a propeller is a fan with 3 or 4 blades. The more propeller blades, the stronger the water pressure or the more power it can create to make the vessel move faster.

The power that the main engine generates and transmits to the propeller is converted from a rotational motion to provide thrust or create thrust. This thrust or propulsive force pushes the ship or the boat forward.

To understand propeller efficiency, you need to understand how it is calculated. Propeller efficiency is the result of dividing the propeller power by the engine power.

propeller-mixers

The basis of ship or boat propelling are Bernoulli’s principle or Bernoulli’s theorem and Newton’s laws, particularly the third law of motion.

If you want to learn technical stuff about how to draw a propeller, I recommend this boat propeller drawing video.

Propeller Drawing

Types of Propellers

Propellers can be: fixed-pitch, controllable-pitch, contra-rotating, and waterjets.

  • Fixed-Pitch Propeller – This type of propeller is the most common propeller you see on recreational boats. This is a strong propeller but there is no option to adjust or match the performance with the running condition.
  • Controllable-Pitch Propeller – This propeller, as the name implies, allows the skipper to make adjustments and tune while the boat is in motion. This propeller is more expensive to buy and maintain.
  • Contra-Rotating Propellers – These are double propellers mounted on a single shaft. Each propeller rotates in opposite directions. These types provide outstanding maneuverability but are less sturdy.
  • Waterjets – Waterjets, which do not have propellers, can drive a boat or ship forward. It works by pumping liquid through a tube that serves as a propeller. These are typically seen on jet skis and speedboats.

Propeller vs Jet

A propeller is characterized by the blades attached to the shaft to facilitate movement. On the other hand, a jet’s power is created by forcing water into a tube. Propeller engines are generally more fuel efficient than jet engines because they provide thrust through a torque.

Propeller vs Turbine

While a propeller generates thrust, a turbine extracts energy. It does the opposite of the propeller. It utilizes mechanical energy to provide electricity.

Other Kinds of Propellers

There are also other kinds of propellers that you might be interested to know. These include, propeller mixers, propeller agitators, and pump propeller or propeller pump.

  • Propeller Mixers – A propeller mixer is a device that aids in mixing and agitating liquids. Moreover, it assists in dissolving and suspending solids within liquids.
  • Propeller Agitator – A propeller agitator is generally a high speed stirrer. These axial flow agitator forces are commonly used for low viscous liquids or preparations of highly concentrated solutions.
  • Propeller Pump – A propeller pump or an axial flow pump. This device creates a linear motion or linear flow path. This pump is generally used in water treatment facilities, chemical plants, or in other agricultural applications.

Propeller Maintenance Tips

Propeller maintenance is very important. Below are some maintenance tips for your propeller:

  • Ensure that the propeller is free from damages like cracks, dents, and corrosion but doing a visual check.
  • Establish a propeller maintenance schedule. This is the time that you will check for any damages and remove any debris.
  • Check the blade pitch. If you notice too much or not enough pitch, it can be an indication that you need to replace the propeller.

Frequently Asked Questions

impeller-meaning

What is the difference between blade and impeller?

Impellers and blades are often treated the same. They may seem similar, but they are technically different. Impellers feature vanes that facilitate their purpose. Blades, on the other hand, are what you see on propellers operating at high speeds.

Is an impeller a water pump?

An impeller is not a water pump. Rather, it is a component of a pump system. In boat engines, an impeller is a component that sucks water into the engine to keep it cool.

Conclusion

There you have the impeller vs propeller comparison. The impeller and propeller are two different components of an engine. An impeller is part of the engine pump of the boat’s engine system that helps avoid overheating.

A propeller is a component that propels water for the boat to move forward. Both components perform a rotational motion to operate.

Maintaining these two components regularly ensures your safety while operating your boat. You can check the detailed impeller and propeller maintenance guide.

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