Yamaha F50D Servise Manual page 52

TECH
FEA
Trim-up function
The gear pump 6 pumps PTT fluid to the up-main valve 7. As a result, the fluid pressure opens
the up-shuttle piston 9 causing the fluid to flow into the lower part of the PTT cylinder 1. At the
same time, vacuum from the gear pump 6 opens the down-main valve 4 and down-shuttle piston
0, which causes fluid from the upper part of the PTT cylinder 1 to return to the gear pump 6, and
also sucks fluid in through the reservoir 8.
The pressurized fluid forces up the trim cylinder 3 along with the tilt piston e, free piston q, and
trim cylinder base w. As the trim cylinder 3 moves up, the PTT ram 2 extends and the outboard
motor is trimmed up. The end of the trim range is when the trim cylinder 3 tops out in the PTT cyl-
inder 1.
a
:
b
:
1 PTT cylinder
2 PTT ram
3 Trim cylinder
4 Down-main valve
5 PTT motor
6 Gear pump
7 Up-main valve
8 Reservoir
9 Up-shuttle piston
2-13
Technical features and description
2
1
3
4
e
q
w
5
6
0
8
0 Down-shuttle piston
q Free piston
w Trim cylinder base
e Tilt piston
a Return
b Send
7 8
9