2001 Mercury Mariner 50-60HP Factory Service Manual, Page 334Get this manual
POWER TRIM
Troubleshooting
Support outboard with tilt lock pin when servicing power trim systemIMPORTANT: After debris or failed components have been found (during troubleshooting procedure), it is recommended that unit be disassembled completely and ALL O-rings be replacedCheck ball valve components and castings must be cleaned using engine cleaner and compressed air or replaced prior to re-assemblyIMPORTANT: Power trim system is pressurizedOutboard must be in the full "UP" position (trim rod fully extended) prior to filldrain plug, or manual release valve removalRefer to instructions following if disassembly is required when servicingFollow preliminary checks before proceeding to troubleshooting flow diagrams (following)