1998 Johnson Evinrude "EC" 25, 35 HP 3-Cylinder Outboards Service Manual, Page 258Get this manual
Component Description [] UP CHECK VALVEWhen opened by pump pressure, it directs fluid to bottom of cylinder to move piston UPWhen opened by pump control piston, it allows low pressure fluid to return to the pump as the piston moves DOWN[] MANUAL RELEASE VALVEWhen opened minimum of three turns, it allows the engine to be manually raised or loweredIt also contains the EXPANSION RELIEF VALVE, which protects the unit from extreme pressures caused by thermal expansion of the fluid
DOWN CHECK VALVEWhen opened by pump pressure, it directs fluid to top of cylinder to move piston DOWNWhen opened by pump control piston, it allows low pressure fluid to return to the pump as the piston moves UPPUMP CONTROL PISTONMoved by pump pressure, it controls the UP and DOWN check valvesTogether, they control fluid direction and cylinder movement