Yamaha F50A Service Manual page 29

Trim-up function
The gear pump pumps power trim and tilt fluid to the up-main valve. As a result, the fluid pressure
opens the up-shuttle piston causing the fluid to flow into the lower part of the power trim and tilt cyl-
inder. At the same time, vacuum from the gear pump opens the down-main valve and down-shuttle
piston, which causes fluid from the upper part of the power trim and tilt cylinder to return to the gear
pump, and also sucks fluid in through the reservoir.
The pressurized fluid forces up the trim cylinder along with the tilt piston, free piston, and trim cylin-
der base. As the trim cylinder moves up, the ram extends and the outboard motor is trimmed up.
The end of the trim range is when the trim cylinder tops out in the power trim and tilt cylinder.
Trim-up function
1
C
1 Power trim and tilt cylinder
2 Ram
3 Trim cylinder
4 Down-main valve
5 Motor
6 Gear pump
7 Up-main valve
8 Reservoir
62Y3A11
5
2
3
4
0
A
B
6
7
8
9
9 Up-shuttle piston
0 Down-shuttle piston
A Free piston
B Trim cylinder base
C Tilt piston
È Return
É Send
Technical tips
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S62Y1390
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