How to Change the Impeller in a Honda 9.9 Outboard

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Honda boat motors are strong and long-lasting motors that come in a variety of sizes. The Honda 9.9 is a sub-ten horsepower motor that puts many motors twice its size to shame. The impeller in this Honda motor is a crucial rubber turbine that circulates water through the motor to keep it cool. The impeller draws water through the engine body, depositing it back into the water body the boat sits in. Changing the impeller is a common maintenance procedure, as, over time, it can become cracked and worn. Any home marine mechanic can tackle this project in an afternoon.

Items you will need

  • Socket wrenches

  • Padded vice

  • Pliers

  • Screwdriver

  • New pump impeller

Use the screwdriver to remove the four mounting screws found on the bottom of the motor shroud, disconnecting the shroud in the process.

Pull the lower shroud off of the motor and locate the silver, bell-shaped water pump housing. Use the socket wrenches to remove the mounting bolts around the corners and slide the housing off of the transmission shaft. Use the pliers to pull the impeller out of the housing.

Place the new impeller into the housing by slowly turning it counterclockwise and slide the housing back down the transmission shaft. Tighten the housing down with the mounting bolts and then slide the lower motor shroud back into place with the bottom of the upper motor shroud. Secure the motor shroud with the mounting screws.


  • Grease the inside of the water pump housing before squeezing the impeller into the housing itself to ensure an easy start-up.
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