How to Adjust Idle Yamaha 40hp


In what way do you alter a Yamaha 40 horsepower idle setting to cause the engine to run smoothly while it’s out of gear? Is there a book or video that provides the correct procedures on how to calibrate idle speed settings? My outboard is running rough at idle speed and occasionally it will stall. The engine also bogs when accelerating.

My Yamaha boat motor is a 2004 two-stroke 3-cylinder. The Yamaha outboard ID plate identifies the engine model number as 40TLRC. Can anyone tell me how to properly fine-tune idle speed adjustment? Thank you!

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Federico Federico Ronzoni 3 years 2021-08-27T00:04:56+00:00 0 Answers 2053 views Beginner 2

Answers ( 3 )


    To adjust engine idle speed be certain the motor is warm and out-of-gear, then turn the throttle stop screw inward to increase the engine’s rotational speed or outward to make the engine idle more slowly.

    Idle speed adjustment procedures might differ for some year and model engines. Go here to download a complete repair manual for any Yamaha outboard engine.

    How to Adjust Idle Yamaha 40 hp Outboard

    2004 Yamaha 40TLRC Idle Speed Adjustment Instructions

    Measure Idle Speed

    1. Run engine until it reaches normal operating temperature.
    2. Attach a tachometer to cylinder #1 high tension lead to measure idle speed rpm.
    3. Factory idle speed specification is 800 ± 50 rpm. Adjust idle if out of specification.

    Adjust Idle Speed

    1. Slightly loosen the throttle stop screw (see image 1) so that you can fully close the throttle valve.
    2. Loosen the throttle lever securing screws (see image 2) of the middle and upper carburetors by rotating the screws clockwise.
    3. Start the engine and allow it to operate for a few minutes or until it reaches normal operating temperature.
    4. Once again connect a tachometer to cylinder #1 high tension lead.
    5. Now adjust the throttle stop screw screw inward or outward until the factory idle speed (800 ± 50 rpm) rpm is achieved.

    • Turning the throttle stop screw in will change idle speed to become higher.
    • Turning the throttle stop screw out will tweak idle speed to become lower.

    To finish things up, while you are lightly pushing the throttle lever of the lower carburetor in the direction of the arrow (fully closed), you must torque the throttle lever securing screw on the middle and upper carbs by turning the screws counterclockwise.

    Best answer

    What is the manual part number for my 2004 Yamaha F40TLRC 4-stroke outboard? The motor is idling unevenly so I need to fine-tune the carb.


    To properly adjust idle speed on a 2004 Yamaha F40TLRC 40 hp outboard you will need the factory service manual (part number LIT-18616-02-16). You can download the complete service repair manual at

    List Of Yamaha Manuals 2000 2004

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