1993 Johnson Evinrude "ET" 90 degrees CV Service Manual, P/N 508285, Page 39Get this manual
Throttle Valve Synchronization
With the engine idling in NEUTRAL, if loosening the carburetor lever adjustment screws results in better idle, improper synchronization of the throttle valves is indicatedAt idle, the throttle valves in all carburetors must be completely closedIf the carburetor linkage is misadjusted so one carburetor throttle plate is slightly open, it will result in poor quality idle1With the engine not running, remove the air silencer cover to observe the throttle valve action2Loosen the throttle cam follower screw Push the throttle cam follower away from the throttle camThe throttle cam follower must not touch the throttle cam during this procedure
1101 3Loosen the lower carburetor lever adjusting screw
4Partially open the throttle shafts and allow them to snap closed to be certain the throttle valves are closedPress downward on tab of the adjusting link to remove backlashTighten the adjusting screwMove the cam follower and check that the throttle shafts start to rotate at the same time