Yamaha F50A Service Manual page 30

GEN
INFO
General information
Trim-down function
When the power trim and tilt switch is pressed to "Down", the motor turns the gear pump counter-
clockwise and the power trim and tilt fluid flows in the opposite direction to that of the trim-up func-
tion.
Tilt-up function
When the trim cylinder tops out, the check valve is pushed down by the end screw wall. This causes
the ball in the check valve to move down, opening the fluid passage and allowing the power trim and
tilt fluid to flow from the upper part of the trim cylinder, through the down-shuttle piston and the
down-main valve, and back to the gear pump. In addition, fluid is also sucked in through the reser-
voir and the pressurized fluid continues to flow into the lower part of the trim cylinder, pushing up the
tilt piston and free piston, and further extending the ram.
As the tilt piston moves up and off of the trim cylinder base, the base moves up and pushes the balls
outward to fit into holes of the power trim and tilt cylinder. Once the balls have been fitted into the
holes the trim cylinder base cannot move.
The end of the tilt-up range is when the tilt piston tops out in the trim cylinder and the ram is fully
extended.
2
The tilt-up function operates when the fluid pressure is under 10 MPa (100 kgf/cm , 1,423 psi).
2
When the fluid pressure in the lower part of the trim cylinder increases to over 10 MPa (100 kgf/cm ,
1,423 psi), the up-relief valve opens and allows the pressurized fluid to flow into the reservoir. Thus,
the tilt piston and free piston are not pushed up and the ram cannot be extend further.
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