1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 274Get this manual
Before the boat is trailered, the operator should check for clearance between the outboard skeg and pavement to prevent damage to skeg from striking pavementIf the outboard must be tilted for clearance between skeg and pavement, device such as "Transom Saver" should be installed to prevent stress to boat transom from outboard weight while the boatoutboard are being trailered Trim "In" Angle Adjustment WARNING
Boat operation with outboard trimmed to the full "In" trim angle [not using the trim angle adjustment bolt (a)] 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 pin (a) 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 (a) may be advantageous to acceleration and planingA water test is required to determine if these characteristics apply to particular boat motor combination