Honda BF35A-BF45A Outboard Motors Shop Manual., Page 226Get this manual
Tilt down operation The motor rotates counterclockwise when the "DOWN" side of the power trimtilt switch is pressed, and the oil flows from the gear pump the spool valveAs this oil moves the spool valve the right and pushes the right side check valve open, the oil in the lower chamber of the cylinder returns the gear pump, oil pressure in the oil passage increases further, left side check valve opens, and the oil flows the upper chamber of the cylinder and pushes the piston down allow the outboard motor tilt downThe oil in the lower chamber of the cylinder passes through the right side check valve and returns the gear pumpAs oil pressure in the upper chamber of the cylinder increases when the outboard is in the full tilt down position, is relieved the down relief valve