Yamaha F150A, Service Manual

Page: 64 / 493

2-19
PTT unit
PTT unit
Trim-up and tilt-up function
Pushing the UP button on the PTT switch causes the PTT motor “1” to activate the gear pump “2”,
generating the PTT fluid pressure. The PTT fluid pressure opens the up-main valve “3” at the same
time pushing the shuttle piston “4”, and this opens the down-main valve “5”.
The PTT fluid passes through the up passage and flows into the lower chambers of the trim cylin-
ders “6” and the lower chamber of the tilt cylinder “7”. The PTT fluid pressure pushes up the trim
rams “8”, and the PTT fluid in the upper chambers of the trim cylinders “6” returns to the reservoir
“9”.
The PTT fluid pressure pushes up the tilt ram “10”, and the PTT fluid in the upper chamber of the tilt
cylinder “7” passes through the down passage, returning to the gear pump. When tilt-up operation is
complete, the PTT fluid pressure increases. When this exceeds 12.2 MPa (122.0 kgf/cm
2
,
1769.0 psi), this causes the up-relief valve “11” to open, releasing the PTT fluid pressure. Addition-
ally, if the PTT fluid pressure is abnormally high exceeding 18.6 MPa (186.0 kgf/cm
2
, 2697.0 psi),
then the protection valve “12” will open to protect the PTT unit.
A. Return
B. Send
1
11
12
5
4
3
7
10
9
8
6
6
2
B
A