Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 296Get this manual
POWER TRIM
Shock Function Up
Oil inside the down cavity is locked in static position by the closed down ci rcuit pressure operated valve (f)the manual release valve (p) and the manifold reverse suction valve (0)If the outboard strikes an underwater object while in forward gear, the piston rod (a) will try to rapidly extend from the cylinder (w)the pressure increases inside the trim cylinder down cavity and connecting passagesWhen the pressure increases to the level required, the impact relief valves (v)located inside the shock piston (u)wi ll open and allow the fluid to pass through the shock pistonAs the fluid passes through the piston, the piston rod (a) will extend from the trim cylinderThe memory piston (t) is held in position by vacuum, created by the oil in the up cavity being locked in static positionTherefore; oil passing through the shock piston is trapped between the memory piston (t) and shock piston (u)