Mercury Optimax Models 135, 150, Direct Fuel Injection., Page 352Get this manual
POWER TRIM
Trim Indicator Gauge Needle Adjustment
1Turn ignition key to "RUN" position2Tilt outboard to full "IN" positionNeedle of trim indicator gauge should be in full "IN" position3If not, tilt outboard to full "OUT" position to gain access to trim sender and engage tilt lock lever4Loosen trim sender screws and reposition trim sender5Tighten trim sender screws