1994 Johnson/Evinrude "ER" 9.9 thru 30 outboards Service Manual, Page 262Get 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
A 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: With the motor shut OFF, loosen the trim tab screwIf the boat pulled to the right, move the rear of the trim tab slightly to the rightIfthe boat pulled to the left, move the rear of the trim tab slightly to the left Tighten the trim tab screw to torque of 60-84 inIbs(7-9 Nm) Test the boat and, if needed, repeat the procedure until steering effort is as equal as possibleHigh motor installationsThe trim tab might be above the water when the motor is trimmed outSteering effort might increaseSteering effort will be reduced if you trim the motor in and submerge the trim tabDual motorsMove both trim tabs equally and in the same direction