Mercury 75 Service Manual page 367

Trim Up
When the trim switch is activated in the up position,
the electric motor (c) begins to rotate the pump gears
(j), the oil pump draws a small amount of oil through
the filter (g) and through the up circuit suction port (i).
The oil pump gear (j) rotation forces oil into the pas-
sages for the up circuit. Oil, under pressure, will slide
the shuttle valve (m) against the down circuit pres-
sure operated valve (f). The shuttle valve will me-
chanically open the down pressure operated valve,
allowing oil from the down cavity of the trim cylinder,
to flow into the oil pump. This returning oil, from the
down cavity, will supply most of the oil required for the
up circuit. Oil in the up circuit is blocked from return-
ing into the reservoir by the ball inside the down cir-
cuit suction port (k). The pressure of the oil will force
the up circuit pressure operated valve (n) to open, al-
lowing the oil to enter the passages inside the man-
ifold (q) leading to the trim cylinder (w) up cavity. Oil
is blocked from all other passages by the closed
manual tilt valve (p). Oil under pressure will enter the
trim cylinder below the memory piston (t). With an in-
creasing amount of oil entering the cylinder, the
memory piston contacts the shock piston (u) and
forces the piston rod (a) up and out, raising the out-
board motor. Oil on the top of the shock piston exits
through a passage running down along the side of
the cylinder and enters the manifold passages. The
oil is drawn back into the pump (j) through the open
down pressure operated valve (f) and enters the
pump as supply for the up circuit.
90-830234R3 DECEMBER 1997 MID-SECTION - 5C-7