Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 301Get this manual
POWER TRIM
Troubleshooting
Support outboard with ti lt lock pin when servicing power trim system
IMPORTANT: 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 fullUP" position (trim rod fully extended) prior to filVdrain plug, or manual release valve removalRefer to instructions following if disassembly is required when servicing Follow preliminary checks before proceeding to troubleshooting flow diagrams (following)