Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 256Get this manual
Hydraulic System Troubleshooting Support outboard with tilt lock lever 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 ballvalve components and castings must be cleaned using engine cleaner and compressed air or replaced prior to reassemblyIMPORTANT: 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 servicing FollOW preliminary checks before proceeding to troubleshooting flow diagrams (following)