2009 Yamaha F40 Outboard Service Manual, Page 53Get this manual
PTT unit
Tilt up operation
When the PTT switch is pressed to "UP," fluid pressure created by the gear pump flows into the up side of the shuttle piston and pushes the up valve allowing it to openAt this point, the fluid pressure forces the shuttle piston to slide to the down valve bThe protrusion of the shuttle piston opens the down valve b, which opens the return circuitThen, the PTT fluid flows into the lower chamber of the cylinder to force the free piston and the tilt ram assembly to move upwardThe relief valve of the fluid pressure circuit will open when the fluid pressure exceeds the limit, while the relief valve in the upstream will not work in its trim range because the passage is closed with the free piston rubber seal gThe up-relief valve opens at 5.4 MPa (54.0 kgfcm2, 783.0 psi)