Yamaha F50D Servise Manual page 55

Stopping condition
When the PTT switch is not pushed (released), the gear pump does not pump the fluid, the up-main
valve and the down-main valve are closed, and the PTT fluid pressure in the system remains con-
stant. This allows the ram to maintain its position until the PTT fluid flows through the system again.
When the outboard motor hits something in the water
The check valve of the trim cylinder 2 and the tilt piston absorber 4 of the tilt piston 5 help to pre-
vent internal damage to the PTT unit and help to protect the bracket and lower unit from damage in
case the outboard motor hits something during operation.
When the outboard motor hits something, highly pressurized fluid in the upper part of the PTT cylin-
der 1 pushes down the check valve 7 of the trim cylinder 2. At the same time, fluid pressure in
the upper part of the trim cylinder 2 increases and the tilt piston absorber 4 is pushed down. As a
result, the tilt piston 5 and the PTT ram 3 are pushed up without the free piston 6. The tilt piston
5 is stopped before reaching the top of the trim cylinder 2 by the damper function of the tilt piston
absorber 4 to protect the PTT unit from damage.
å
1
2
3
4
5
6
:
:
å PTT fluid pushes down the check valve.
∫ Tilt piston and PTT ram are pushed up.
1 PTT cylinder
2 Trim cylinder
3 PTT ram
4 Tilt piston absorber
∫
7
4
6
5 Tilt piston
6 Free piston
7 Check valve
a Send
b Moving direction
PTT unit
5
2-16
0
1
2
3
4
5
6
7
8
9
10
A