Mercury 225 EFI, Service Manual

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POWER TRIM - DESIGN II
Page 5B-12 90-884294 OCTOBER 2001
Trim Circuit
When the up button is activated the electric motor (1) will rotate the oil pump gears (2).
As the oil pump gears begin to rotate, oil is drawn through the up circuit suction check
valve (3) and into the pump, supplying flow for the up circuit. Oil under pressure opens
the up circuit pressure operated valve (8), allowing oil enter the up pressure passages
inside the manifold casting. The oil continues on through the up passages into the bottom
of the cylinders below the pistons, pushing the trim (9) and tilt (10) rams up and out. Oil,
from the pump, is blocked from returning into the reservoir by the closed down suction
check valve (4). Oil, under pressure slides the shuttle spool (5) to the left, against the down
circuit pressure operated valve (6). The shuttle spool will mechanically open the down
pressure operated valve, allowing oil to return into the pump from top of the tilt cylinder
(7). Oil returning from the top side of the tilt cylinder piston flows through an interconnect-
ing passage on the side of the tilt cylinder, through the lower pivot pin (12), past the open
down pressure operated valve, and into the pump, supplying some of the oil required for
the up circuit. Oil returns into the reservoir (11), from the trim rams, through passages cast
inside of the manifold.
Up pressure varies from 850 psi to 1150 psi unloaded to approximately 3000 psi against
full engine thrust.