Yamaha F150B Service Manual

Also see for F150B: Owner's manual Service manual Owner's manual

2-32PTT unit012345678910AStationary conditionWhen the PTT switch is not pressed, the gear pump will not pump the fluid, the up-main valve andthe down-main valve will remain closed, and the PTT unit in the system remains constant. This willallow the tilt ram and the trim ram to maintain their positions until the PTT fluid flows through thesystem again.When the outboard hits something in the waterIf the lower casing comes in contact with an obstacle while the boat is in operation, a sudden exten-sion force becomes applied to the tilt ram. This force causes the fluid pressure in the tilt cylinderupper chamber to increase, and the tilt piston absorber to open and release the fluid pressure intothe space between the tilt piston and the free piston. As a result, the damping effect of the tilt pistonabsorber and the oil lock mechanism prevent the PTT unit from damage, before the tilt piston comesin contact with the top of the tilt cylinder.After the collision, a force to return the outboard motor to its original position is generated due to theweight of the outboard motor and the thrust of the propeller.The PTT fluid passes through the shock return valve of the tilt piston, via the free piston, and into thetilt cylinder upper chamber.When the tilt piston comes in contact with the free piston, the tilt piston stops.A The outboard motor hit the object.B The outboard motor returned to the originalposition.a Tilt ramb Tilt cylinderc Tilt piston absorberd Tilt pistone Shock return valvef Free pistonabcd efA B