Mercury 40 Service Manual page 252

SHOCK FUNCTION UP
Oil inside the down cavity is locked in a static position
by the down pressure operated valve (h), the manual
release valve (j) and the tilt relief valve (k). If the out-
board strikes an underwater object while in forward
gear the trim ram (b) will try to rapidly extend from the
cylinder, the pressure increases inside the trim cylin-
der down cavity and connecting passages. The rise
in pressure will seat the check ball (r) inside the suc-
tion seat (g), preventing fluid from returning into the
reservoir. When the pressure increases to the level
required, the impact relief valve (c), located inside the
shock piston (d), will open and allow the fluid to pass
through the shock piston. As the fluid passes through
the piston, the trim ram (b) will extend from the trim
cylinder. The memory piston (e) is held in position by
vacuum, created by the oil in the up cavity being
locked in a static position. Therefore; oil passing
through the trim ram piston is trapped between the
memory piston (e) and shock piston (d).
90-852572R1 JANUARY 1998 MID-SECTION - 5C-15