Down Mode - Mercury 40 Service Manual

DOWN MODE

When the trim switch is activated in the down posi-
tion, the electric motor (a) will rotate the pump (n) in
the opposite direction. With the pump gears rotating
backwards, the flow of oil is reversed. Oil is drawn
through the filter, past the feed check valve (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 operated valve (l). The shuttle valve
will mechanically open the pressure operated valve
and allow oil, from the up cavity of the manifold (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 valve.
Oil, under pressure, opens the 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 cylin-
der. The cavity, inside the cylinder, above the shock
piston (d) is the down cavity. As the down cavity fills
with oil, the trim ram (b) retracts into the cylinder, low-
ering the outboard motor. Oil from the up cavity exits
the cylinder and is drawn back into the pump through
the up pressure operated valve (l). When the trim ram
reaches full travel, the oil pressure inside the down
circuit will rise until the down pressure regulation
valve (q) opens, bypassing oil back into the reser-
voir(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 pressure regulating valve (q) will close. The
closed valves will lock the fluid on either side of the
shock piston (d), holding the outboard motor in posi-
tion.
90-852572R1 JANUARY 1998 MID-SECTION - 5C-13