1998 Johnson Evinrude "EC" 9.9 thru 30 HP 2-Cylinder Outboards Service Manual, Page 250Get this manual
Trim Tab Adjustment20, 25, 30
Improper trim tab adjustment can cause difficult steering
A propeller will generate steering torque when the propeller shaft is not running parallel to the water's surfaceThe trim tab is adjustable to compensate for this steering torque
Important single trim tab adjustment will relieve steering effort under only one set of speed, motor angle, and load conditionsNo single adjustment can relieve steering effort under all speed, motor angle, and load conditionsIf the boat pulls to the left or right when its load is evenly distributed, adjust the trim tab as follows:
OJ With the motor shut OFF, loosen the trim tab screwIf