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How to adjust an outboard carburetor

Updated February 21, 2017

Adjusting the outboard carburettor is a job you can do in just a few minutes, helping to extend the life of your outboard motor. The outboard carburettor has two adjustment screws on its barrel that can be set with a screwdriver and a vacuum gauge. The optimum setting for the low-speed adjustment screw for the outboard carburettor is 750rpm. Gain access to the carburettor by removing the motor housing on the top of the motor.

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  1. Lift the motor housing off the top of the outboard motor and set it aside. Start the motor and let it warm up for about five minutes.

  2. Remove the rubber vacuum hose from the vacuum port at the base of the carburettor barrel and connect a vacuum gauge to the vacuum port. Locate the two adjustment screws on the sides of the carburettor barrel and move the throttle cable on the carburettor so the engine is running wide open.

  3. Adjust the high-speed jet screw on the left side of the carburettor with a screwdriver a half-turn at a time until the engine is running smoothly. Give the engine about 20 seconds between each turn to let it even out. Follow the rpm reading on the vacuum gauge needle to determine which direction to turn the adjustment screw.

  4. Adjust the low-speed jet screw on the right side of the carburettor with a screwdriver, turning the screw a half-turn every 20 seconds until the vacuum gauge is reading about 750rpm. Remove the vacuum gauge from the vacuum port and reattach the rubber vacuum hose.

  5. Shut the outboard motor off and reattach the motor housing to the top of the motor.

  6. Warning

    To avoid burns, always be careful of touching the outboard motor engine while adjusting the carburettor.

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Things You'll Need

  • Screwdriver
  • Vacuum gauge

About the Author

Carl Pruit has been a freelance writer since 2005, specializing in service journalism and travel. His work has appeared on various websites. Born and raised in California, Pruit attended Contra Costa Community College in San Pablo, Calif. and received an associate degree in the administration of justice.

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