2001 Mercury Mariner 50-60HP Factory Service Manual, Page 327Get this manual
POWER TRIM
Down Mode
When the trim switch is activated in the down position, the electric motor (c) will rotate the pump (j) in the opposite directionWith the oil pump gears rotating backwards, the flow of oil is reversedOil is drawn through the filter (g), through the down circuit suction port (k) and into the oil pump (j)The pump forces pressurized oil into the down passages, oil will slide the shuttle valve (m) into the up circuit pressure operated valve (n)The shuttle valve will mechanically open the up circuit pressure operated valve and allow oil, from the up cavity of the trim cylinder (w), to return into the oil pumpThis returning oil, from the up cavity, will supply the oil required for the down circuitThe oil is blocked from returning into the reservoir by the ball (i) inside the up circuit suction portOil, under pressure, opens the down circuit pressure operated valve (f) and enters the down passages inside of the manifold (q)The manifold passage connects into the trim cylinder passage leading to the top of the cylinderThe cavity, inside the cylinder, above the shock piston (u) is the down cavityAs the down cavity fills with oil, the piston rod (a) retracts into the cylinder, lowering the outboard motorOil from the up cavity exits the cylinder and is drawn back into the pump through the open up circuit pressure operated valve (n)When the piston rod reached full travel, the oil pressure inside the down circuit will rise until the down pressure regulating valve (e) opens, bypassing oil back into the reservoirWhen the trim button is released, and the oil pump stops supplying pressure, both of the pressure operated valves (fn) will close and; if open, the down pressure relief valve (e) will closeThe closed valves will lock the fluid on either side of the shock piston (u)memory piston (t), holding the outboard motor in position