2001 Edition Yamaha F225A and LF225A Outboards Service Manual, Page 30Get this manual
GEN INFO
General information
Stationary condition When the PTT switch is not pressed, the gear pump will not pump the fluid, the up-main valve and the down-main valve will remain closed, and the PTT unit in the system remains constantThis will allow the tilt ram and the trim ram to maintain their positions until the PTT fluid flows through the system againWhen the outboard hits something in the water If the lower casing comes in contact with an obstacle while the boat is in operation, sudden extension force becomes applied to the tilt ramThis force causes the fluid pressure in the tilt cylinder upper chamber to increase, and the tilt piston absorber to open and release the fluid pressure into the space between the tilt piston and the free pistonAs result, the dampening effect of the tilt piston absorber and the oil lock mechanism prevent the PTT unit from damage, before the tilt piston comes in contact with the top of the tilt cylinderAfter the collision, force to return the outboard motor to its original position is generated due to the weight of the outboard and the thrust of the propellerThe PTT fluid passes through the shock return valve of the tilt piston, via the free piston, and into the tilt cylinder upper chamberWhen the tilt piston comes in contact with the free piston, the tilt piston stops