Yamaha F100B F100C Outboards Factory Service Manual, Page 64Get this manual
Periodic checks and adjustments
3Attach the special service tool to hightension cord #1 1
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Digital tachometer: 90890-06760
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Engine idle speed: 800900 rmin 3Turn the throttle stop screw in direction or until the specified engine idle speed is obtainedS60C3480
Timing light: 90890-03141 4Check that the ignition timing mark (5) on the flywheel magnet is aligned with the pointer bCheck the ignition system and ignition control system if necessary
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NOTE: To increase the idle speed, turn the throttle stop screw in direction To decrease the idle speed, turn the throttle stop screw in direction b4After adjusting the idle speed, rev the engine few times and let it idle for at least 15 seconds to check the stability of the engine