Yamaha F150A, Service Manual

Page: 65 / 493

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PTT unit
0
1
2
3
4
5
6
7
8
9
10
A
Trim-down and tilt-down function
Pushing the DN 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 down-main valve “3” at the
same time pushing the shuttle piston “4”, and this opens the up-main valve “5”.
The PTT fluid passes through the down passage and flows into the upper chamber of the tilt cylinder
“6”. The PTT fluid pressure pushes down the tilt ram “7”, and the PTT fluid in the lower chamber of
the tilt cylinder “6” returns to the gear pump “2”.
When the tilt ram “7” drops, the trim rams “8” are pushed down due to the weight of the outboard
motor, and the PTT fluid is sucked up from the reservoir “9” to the upper chamber of the trim cylin-
ders “10”.
When tilt-down operation is complete, the PTT fluid pressure increases. When this exceeds 7.35
MPa (73.5 kgf/cm
2 , 1065.8 psi), this causes the down-relief valve “11” to open, releasing the PTT
fluid pressure. Additionally, if the PTT fluid pressure is abnormally high exceeding 26.5 MPa
(26.5 kgf/cm
2 , 384.3 psi), then the protection valve “12” will open to protect the PTT unit.
A. Return B. Send
1
11
12
3
4
5
2
6
7
9
10
B
A
8
10