Yamaha F150B, Service Manual

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2-31
TECH
FEA
Technical features and description
Trim-down and tilt-down function
When the PTT switch is pressed to “DN,” the power trim and tilt motor operates the gear pump and
fluid pressure is generated. As a result, the fluid pressure pushes the down-shuttle piston, enters
the tilt cylinder upper chamber through the down-main valve, and then pushes the tilt ram down-
ward.
In addition, the fluid pushes the up-shuttle piston to open the up-main valve.
The gear pump draws the PTT fluid from the tilt cylinder and trim cylinder lower chambers, and then
retracts the tilt ram and the trim ram.
Since the fluid pressure from the gear pump is applied to the tilt cylinder upper chamber, the tilt ram
moves downward first.
When the outboard motor comes in contact with the trim ram, the trim ram moves downward simul-
taneously with the tilt ram, due to its own weight and the suction of the PTT fluid by the trim cylinder
lower chamber.
A
Return
B
Send
a
Tilt cylinder
b
Trim cylinder
c
Down-shuttle piston
d
Down-main valve
e
Up-shuttle piston
f
Up-main valve
g
Tilt ram
h
Trim ram
i
Down-relief valve
j
Reservoir
k
Gear pump
l
PTT motor
j
k
l
k
c
b
i
b
g
h
h
e
f
a
d
A
B