Evinrude carburetor adjustments should be made with the motor on the boat and underway. A second boater is required to navigate and control the vessel while you make the adjustments. These adjustments require you to work in close proximity to the engine's moving parts, which poses potential safety risks. Only attempt the adjustments on clear days and in calm waters.
Items you will need
Shop tachometer
Assistant
Screwdriver
Set the shop tachometer to the two-cycle setting. Connect the tachometer to the primary lead for the ignition coil. Tell your assistant to start the motor and run it at half-throttle in "Forward" until it warms up to its normal operating temperature.
Tell your assistant to reduce the throttle setting to "Idle." Turn the idle speed adjustment screw with a screwdriver until the shop tachometer indicates that the engine is running in the correct r.p.m. range, 1,000 to 1,300. Allow at least 15 seconds between each turn of the idle speed adjustment screw.
Confirm the idle speed adjustment is correct by running the engine at various throttle positions. If the engine is running too rich it will "bog down" when the throttle is advanced more than two-thirds throttle, and the idle will be higher than the target idle speed. Since the idle adjustment screw also controls the mixture, readjust the idle speed and repeat the test until the idle speed is correct and the motor no longer "stumbles" during rapid acceleration.