Mercury 40 Service Manual page 371

Trim Up
When the trim switch is activated in the up position, the electric motor (c) begins to rotate
the oil 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 pressure operated valve (f). The shuttle valve will mechanically open the down pres-
sure 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 returning into the reservoir by the ball inside
the down circuit suction port (k). The pressure of the oil will force the up circuit pressure oper-
ated valve (n) to open, allowing the oil to enter the passages inside the manifold (q) leading
to the trim cylinder (w) up cavity. Oil is blocked from all other passages by the closed manual
release valve (p). Oil under pressure will enter the trim cylinder below the memory piston
(t). With an increasing amount of oil entering the cylinder, the memory piston contacts the
shock piston (u) and forces the trim rod (a) up and out, raising the outboard motor. Oil on
the top of the shock piston exits through a passage running down along the side of the cylin-
der and enters the manifold passages. The oil is drawn back into the pump (j) through the
open down circuit pressure operated valve (f) and enters the pump as supply for the up cir-
cuit.
a -
b -
c -
d -
e -
g -
h -
k -
m -
n -
o -
p -
q -
s -
u -
v -
w -
90-828631R3 MARCH 1999
Trim Rod
End Cap
Electric Motor
Reservoir Oil
Down Circuit Pressure Relief Valve
f - Down Circuit Pressure Operated Valve
Filter (2 shown for clarity)
Shock Return Valve
i - Up Circuit Suction Port
j - Oil Pump Gears
Down Circuit Suction Port
l - Oil Fill Cap
Shuttle Valve
Up Circuit Pressure Operated Valve
Manifold Reverse Suction Valve
Manual Release Valve
Manifold
r - Tilt Relief Valve
Tilt Relief Piston
t - Memory Piston
Shock Piston
Impact Relief Valve
Cylinder
POWER TRIM
Page 5C-9