Replacing a boat's impeller: here's how to do it yourself

A properly functioning impeller is essential for cooling your boat's engine. Timely impeller replacement prevents overheating and costly repairs. Fortunately, replacing an impeller is a job you can do yourself with proper instructions. Want to know more about impeller replacement? Then be sure to read on.

This blog in brief:

• Replacing the impeller a crucial part of engine maintenance.
• With the right steps and tools, you can do this yourself.
• Regular maintenance prevents engine damage and saves costs.

What is an impeller and why do you need to replace it?

The impeller is a rubber impeller in your boat engine's water pump. It circulates cooling water, which is essential for keeping the engine at the right temperature. Over time, the impeller wears out from use and may crack or lose pieces. A worn impeller leads to insufficient cooling and an overheated engine. This will prevent you from sailing further and may even damage your engine.

When should you replace the impeller?

It is recommended that the impeller be inspected annually and replaced at least every two years, depending on use and conditions. Signs that the impeller needs replacement include reduced water flow, irregular cooling water discharge or increased engine temperature. If you sail frequently in sandy or polluted waters, the impeller may wear out faster. Regular inspection prevents unexpected problems.

How do you replace the impeller of an outboard motor?

Replacing the impeller on an outboard motor is easy to do with a little technical knowledge. Follow these steps carefully to get the job done successfully.

• Remove the tailpiece from the outboard motor.
• Unscrew the pump housing cover and carefully remove the gasket.
• Once the pump housing is open, you easily slide the impeller off the shaft.
• Coat the new impeller and gasket with acid-free Vaseline and place it back over the shaft. Remember to keep the spigot in place. You can stick this on with Vaseline to make assembly easier.
• Check that the gasket, usually a rubber ring, is on the correct plate.
• Replace the pump housing.
• Replace the tailpiece.

Specific concerns for inboard engines

With inboard engines, such as Volvo Penta or Yanmar engines, it is important to close the cooling water supply valve before you begin. Then you can unscrew the cover of the pump housing. The impeller is best taken out with water pump pliers. Most new impellers come with a new gasket and some Vaseline. Lubricate the new impeller with Vaseline, and replace it. Make sure that the cover and back plate in the housing do not have too deep grooves, otherwise the pump will lose its operation. If this is in order, the cover can be replaced. Do not forget to open the cooling water valve. Does your boat have a weir pot? Then it is always a good idea to fill it with water.

Carefree boating after replacing your impeller

Have you replaced or had your impeller replaced yourself and want to be sure you won't have any surprises in the event of a breakdown along the way? Then consider a Vaarzeker subscription. This way you are always assured of help on the water, even if your impeller or engine unexpectedly fails.

With Vaarzeker you benefit from:

• Immediate assistance with engine breakdowns, even if you have just serviced yourself
• Repairs on site or in port, without towing
• Expert telephone advice for technical questions
• Transparent rates: pay only for material costs

From only €19 per month you can sail the Dutch inland waterways, lakes and the Wadden Sea with peace of mind. View our subscriptions and choose the security that suits you. Do you still have questions? Then feel free to contact with us, our team is ready for you.

Frequently asked questions (FAQ)

How do I know if my impeller is worn out?

Signs of wear include reduced water flow, irregular cooling water discharge and increased engine temperature. Steam from the exhaust is also a sign.

Can I replace the impeller myself?

Yes, with proper instructions and tools, replacing the impeller is a job you can do yourself.

How often should I replace the impeller?

It is recommended that the impeller be inspected annually and replaced at least every two years, depending on use and conditions.

What happens if I don't replace the impeller?

A worn impeller can lead to insufficient cooling, causing overheating and serious engine damage.

Where can I buy a new impeller?

Most water sports stores supply fine aftermarket impellers. Need a new one? Consider ordering two right away so you have one spare.