1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 226Get this manual
Tilting Outboard Manually WARNING Before opening the manual release valve knob, insure all persons are clear of outboard as outboard will drop to full "Down" when valve is openedThe outboard can be raised or lowered manually by opening the manual release valve to turns counterclockwiseClose manual release valve to hold outboard at the desired tilt position
Trim "In" Angle Adjustment WARNING
Boat operation with outboard trimmed to the full "In" trim angle [not using the trim angle adjustment bolt] at planing speed may result in undesirable andor unsafe steering conditionsA water test for handlingsteering conditions is required after any trim angle adjustmentsIMPORTANT: Some boatmotor combinations not using the trim angle adjustment bolt and trimmed to the full "In" trim angle position may not exhibit any undesirable andor unsafe handling andor steering characteristics at planing speedIf so, not using the trim angle adjustment bolt may be advantageous to acceleration and planingA water test is required to determine if these characteristics apply to particular boatmotor combination