Mercury 40 Service Manual page 326

Trim Down
When the trim switch is activated in the down position, the electric motor (a) will rotate the
oil pump gears (n) in the opposite direction. With the oil pump gears rotating backwards, the
flow of oil is reversed. Oil is drawn through the filter, past the up circuit feed check ball (m),
into the down circuit oil pick-up and finally into the oil pump. The pump feeds pressurized
oil into the down passages, oil will slide the shuttle valve (p) into the up circuit pressure oper-
ated valve (l). The shuttle valve will mechanically open the pressure operated valve and al-
low oil, from the up cavity of the trim cylinder (f), to return into the oil pump. This returning
oil, from the up cavity, will supply the oil required for the down circuit. The oil is blocked from
returning into the reservoir by the shuttle valve (p) inside the up circuit feed check ball. Oil,
under pressure, opens the down circuit pressure operated valve (h) and enters the down
passages inside of the manifold (f). The manifold passage connects into the trim cylinder
passage leading to the top of the cylinder. The cavity, inside the cylinder, above the shock
piston (d) is the down cavity. As the down cavity fills with oil, the trim rod (b) retracts into the
cylinder, lowering the outboard motor. Oil from the up cavity exits the cylinder and is drawn
back into the pump through the opened up circuit pressure operated valve (l). When the trim
rod reaches full travel, the oil pressure inside the down circuit will rise until the down circuit
pressure relief valve (q) opens, bypassing oil back into the reservoir(t). When the trim button
is released, and the oil pump stops supplying pressure, both of the pressure operated valves
(h & l) will close and; if open, the down circuit pressure relief valve (q) will close. The closed
valves will lock the fluid on either side of the shock piston (d), holding the outboard motor
in position.
a -
b -
c -
d -
e -
g -
h -
k -
m -
n -
o -
p -
q -
s -
u -
v -
w -
90-828631R3 MARCH 1999
Electric Motor
Trim Rod
Impact Relief Valve
Shock Piston
Memory Piston
f - Manifold
Suction Valve
Down Circuit Pressure Operated Valve
i - Tilt Relief Actuator
j - Manual Release Valve
Tilt Relief Valve
l - Up Circuit Pressure Operated Valve
Down Circuit Feed Check Ball
Oil Pump Gears
Up Circuit Feed Check Ball
Shuttle Valve
Down Circuit Pressure Relief Valve
r - Check Ball
Reservoir Oil
t - Oil Reservoir
Oil Fill Cap
Shock Return Valve
Filter
POWER TRIM
Page 5B-17