Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 300Get this manual
POWER TRIM
Manual Tilt
To manually tilt the outboard engine, the owner will need to back out the manual release valve (p) 3-4 turns With the valve backed out, the internal passages inside the manifold are connected togetherThese passages connect both the cylinder down and up cavities together, along with the reservoir, allowing the engine to be raised or loweredPiston rod (a) movement will continue until the manual release valve (p) is closedlocking the fluid inside of the cylinder and manifold