1985 OMC 65, 100 and 155 HP Models Commercial Service Manual, PN 507450-D, Page 386Get this manual
4Oil returning from the bottom of the trim cylinders flows through the trim check valve which the pump control piston is holding open and then back to the input of the pump5Because of the volume of the tilt and trim rods, less oil volume is required above the tilt or trim pistons than is being supplied to the pump from beneath the pistonsSome of the oil from the outlet side of the pump is returned to the reservoir through the trim down pump relief valve and in doing so, reduces the volume of oil flowing into the cylinders The piston movement is then controlled so that the oil returning to the pump equals the combination of the oil flow to the cylinders plus the oil flowing to the reservoir through the trim down pump relief valve6If the switch is held in the down position after the trim and tilt rods are retracted, the pressure buildup will open the trim down pump relief valve and the fluid will be bypassed back to the reservoirThis valve opens at approximately 4200 kPa (800 psi) Running Forward