Honda Outboards BF40A/BF50A Service Manual, Page 225Get this manual
HONDA BF3SA45A
Hydraulic circuit
Tilt up operation
The motor rotates clockwise when the "UP" side of the power trimtilt switch is pressed, and the oil flows from the gear pump to the spool valveAs this oil moves the spool valve to the left and pushes the left side check valve open, the oil in the upper chamber of the cylinder returns to the gear pump, oil pressure in the oil passage increases further, right side check valve opens, and the oil flows to the lower chamber of the cylinder and pushes the piston up to allow the outboard motor to tilt upThe oil in the upper chamber of the cylinder passes through the left side check valve and returns to the gear pumpAs oil pressure in the lower chamber of the cylinder increases when the outboard is in the full tilt up position, it is relieved by the up relief valve