1993 Johnson Evinrude "ET" 90 degrees CV Service Manual, P/N 508285, Page 210Get this manual
Trim Tab Adjustment The boat may be slightly easier to steer in one direction or the other due to steering forces or other reasonsTo check this, run the boat in straight line with balanced load in an area where current and wind will not be factor
A single trim tab adjustment will relieve steering effort under only one set of speed, trim, and load conditionsNo single adjustment can relieve steering effort under all speed, trim, and load conditions1Turn the steering wheel in both directions to determine the direction that requires the least amount of steering effort2Loosen the trim tabIf the boat: pulled to port, move the rear of the trim tab to port pulled to starboard, move the rear of the trim tab to starboard