1998 Johnson Evinrude "EC" 90, 100C, 105C, 115, 150, 150C, 175 60 deg. LV Service Manual, P/N 520210, Page 260Get this manual
Trim Tab Adjustment
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 torqueA 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 conditions
Important
If 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 rightIf the boat pulled to the left, move the rear of the trim tab slightly to the left