Yamaha F150B, Service Manual

Page: 73 / 458

2-30
PTT unit
0
1
2
3
4
5
6
7
8
9
10
A
Trim ram retraction function
When the outboard motor is tilted up and held in place with the tilt stop lever and the PTT switch is
pressed to “DN,” the trim ram will be retracted.
Although the gear pump attempts to draw fluid from the tilt cylinder and trim cylinder lower cham-
bers, after the PTT switch has been pressed, fluid cannot be drawn from the tilt cylinder lower cham-
ber because the tilt ram is secured in place by the tilt stop lever. Only the PTT fluid from the trim
cylinder lower chamber can be drawn, and as the fluid pressure decreases, the trim ram retracts into
the trim cylinder. Since the tilt ram is secured in place, the PTT fluid pumped by the gear pump flows
into the tilt cylinder upper chamber to increase fluid pressure. As a result, the down-relief valve
opens, and the PTT fluid is released into the reservoir.
A
Return
B
Send
a
Tilt cylinder
b
Trim cylinder
c
Up-main valve
d
Up-shuttle piston
e
Down-shuttle piston
f
Down-main valve
g
Tilt ram
h
Down-relief valve
i
Trim ram
j
Reservoir
k
Gear pump
l
PTT motor
h
i
i
j
k
k
l
d
e
b
b
f
g
c
a
A
B