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How Often Should a Boat Impeller Be Replaced? Answered

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

how often should a boat impeller be replaced

Impeller malfunction is very common in boating. If your boat’s impeller fails, it can lead to engine damages that are expensive to fix. So, how often should a boat impeller be replaced?

Boat impellers should be replaced after 300 hours or every 3 years or when you notice obvious damage.

Although the ideal timing for replacing your boat’s impeller is 3 years, you need to do a regular maintenance check, especially if you do not use your boat often.

How Often Should Replace the Boat Impeller?

Experts suggest that a boat impeller should be replaced after 300 hours of use or every three years, whichever comes first.

Doing this ensures a healthy engine and safe boating.

A boat impeller failure could lead to bigger engine troubles and expensive maintenance. You should check the condition of your impeller if you start noticing failure symptoms.

A regular checkup would help you avoid serious issues.

And, you don’t need to wait until you use it for 300 hours or 3 years to replace the impeller. The replacement cost with parts included will be from $100 to $300, depending on the service that you visit.

How to Tell if Your Boat Impeller Needs to Be Replaced?

As a boater, you need to know the signs of a bad impeller in outboard to determine whether it requires replacement. Many signs help you tell whether your boat’s impeller needs replacement.

  • Frequent Overheating


Suppose your engine’s temperature rises above its normal level, which is 160°F for a gasoline engine and 200°F for a Diesel engine. In that case, the boat’s impeller is probably failing.

The impeller of your boat is the component that keeps your engine cool. A poor impeller performance could lead to an overheating engine.

  • Reduced Outboard Performance

Irregular outboard performance could also mean that your impeller has gone bad. The common issue that boaters observe is the outboard not throttling up. The system issues in the outboard could also lead to overheating and poor overall performance.

  • Impeller Physical Damage or Wear & Tear


If you have not taken your boat out for a very long time, never miss checking the impeller, as it may have lost its flexibility. Check if the impeller has cracks or is worn out.

  • Hollow sound from the engine


If you notice the hollow and somewhat louder sound of your engine, it might signal that the impeller is not working well.

What Causes Your Boat Impeller to Wear Out?


Knowing the causes of impeller wear and tear will give you an idea of why they fail. There are many possible reasons, but I will focus on the most common. These include cavitation, erosion, and corrosion.

  • Cavitation

Cavitation is among the great enemies of your boat’s impeller. The changing pressure level of the pumped liquid is the common culprit of cavitation.

Cavitation is dangerous because this can cause disintegration. The fun is over when your boat’s impeller disintegrates while you’re boating.

  • Erosion

This problem does not happen overnight. This is a gradual process of wearing due to small hard particles, such as sand, that reaches the impeller when the pump sucks water into the housing.

You can minimize it by adjusting the flow velocity in the pump. If this sounds very technical to you, you might need the help of a boat expert.

  • Corrosion

Corrosion occurs when the pH level is extremely low, causing the impeller to deteriorate.

  • Poor Impeller Lubrication

During the inspection, your outboard impeller can dry out if you do not lubricate it. You can use any lubricants available in the market or a dishwashing liquid.

  • Chemical Reaction

When your boat’s impeller gets in contact with chemicals in the water, there is a tendency that a chemical reaction can occur. The common chemicals your boat can pump in are chlorine and sodium hypochlorite.

These chemicals can react negatively with the impeller material and cause damage.

Frequently Asked Questions


Why do you need to replace the impeller on your boat?

Boat impellers wear out like the tires on your car. To keep your boating adventure safe, changing impeller regularly is necessary when you notice any physical damage.

Raw water pump impeller replacement is critical because this component will give you a headache when it fails.

Knowing how to check a broken impeller outboard on a Mercury outboard or any engine gives you the advantage of minimizing the cost to replace an impeller on a boat.

When should you replace your boat impeller?

You will find various guides online on the timing of replacing your boat’s impeller. However, boating enthusiasts suggest that the perfect time to replace the impeller is when you use it for 300 hours or 3 years, whichever comes first.

It’s the same if you want to change impeller on mercruiser or West Marine boat.

What happens if your boat impeller fails?

If the impeller of your boat fails, you will face multiple possible issues. The first thing you will notice is an overheating engine. A simple impeller failure could lead to bigger engine problems if you ignore the symptoms.

How do you replace a boat impeller?

You first need to switch off the power to the pump and uninstall/disconnect its components, including the drain plug, suction hose, shaft guard, casing, and O-ring. Unscrew the old impeller, install the new one, and then put back all the components.

What is the right thing to do?

  • Conduct Regular Check Up

A regular checkup would help you avoid serious issues. If, upon checking, you notice a physical impeller problem, do the necessary boat impeller replacement.

  • Take Your Boat Out

Boaters agree that using their boat often is better. You might find your boat impeller losing its flexibility or getting stiff after months of not boating.

How Many Impellers Does a Boat Have?

Depending on its size, a boat could have at most seven impellers. Still, outboard motor impellers are usually the components that require replacement.


The answer to the question of how often should a boat impeller be replaced varies. But as a boat owner, you should regularly replace your boat’s impeller.

However, you must know the basic symptoms of a failing impeller. It only sometimes follows that your impeller could last 3 years because there are other factors to consider. These factors include the impeller’s frequency of use and wear and tear.

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