1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 319Get this manual
Troubleshooting Flow Diagram Outboard falls to full down position with manual release valve closedExample a: Outboard lowers more than one tilt bolt hole in eight hoursExample b: Outboard during accelerationlowers
Inspect Manual Release ValveResult Result
Manual release valve andor O-ring damage
Manual release valve and O-rings appear to be OKReplace O-rings
Replace defective valve and O-ringsResult
O-rings appear to be OKCylinder bore and memory piston are OKReplace O-rings and proceedInspect O-rings on Pilot Relief Valve (located in manifold assembly)Result Result