Yamaha F50 Service Manual

62Y3A111-16
1
2
3
4
5
6
7
8
I
Operation
When the throttle is opened suddenly, diaphragm 1 (via the link that is connected to the throttle
lever) operates to pressurize the air in the pump chamber. The pressurized air opens diaphragm 2,
and becomes distributed to the carburetors by passing through the pipes that are connected to the
carburetors. The pressurized and distributed air then utilizes the passage of the main air jet to flow
into the main nozzle. The pressure of the air helps suck fuel from the...

GEN 
INFO
General information
1-1762Y3A11
Ignition system
In order to determine the optimal ignition timing that is necessary for the proper operation of the
engine, the built-in microcomputer in the CDI unit detects the signals from various types of sensors
and controls the ignition timing in accordance with a control map that is based on those signals. The
microcomputer also effects controls to protect the engine against overheating, over-revolution, and
oil pressure drops, as well as to control...

62Y3A111-18
1
2
3
4
5
6
7
8
I
Pulser coil
The pulser coil transmits the pulser signals, which are generated in the pulser coil in accordance
with the rotation of the flywheel, to the CDI unit. Among the two protrusions that are provided for
generating signals, one is used for cylinders #1 and #4, and the other for cylinders #2 and #3, thus
enabling the pulser coil to simultaneously ignite two cylinders.
To provide ignition signals to the cylinders, the microcomputer determines the ignition cylinder and...

GEN 
INFO
General information
1-1962Y3A11
Ignition timing control
Control circuit diagram
Basic control
The ignition timing is determined by using the map based on the engine speed (r/min). Then, igni-
tion signals are output from the microcomputer in accordance with the ignition timing map so that
ignition can take place at the optimal timing in relation to the engine speed. Then, the microcom-
puter corrects the ignition timing in accordance with the operating conditions of the engine as
detected by...

62Y3A111-20
1
2
3
4
5
6
7
8
I
Starting control
When starting the engine, the timing is set to 5° BTDC until the crankshaft speed maintains 600
r/min for two seconds or longer.
1Cylinder identification protrusion
2Protrusion for cylinders #1 and #4
3Pulser coil
4Protrusion for cylinders #2 and #3
5Pulser coil signal
6Cylinder identification signal7Starting signal (5° BTDC) for cylinders #1 and 
#4
8Starting signal (5° BTDC) for cylinders #2 and 
#3
9Rotating direction
Warm-up control
After the starting...

GEN 
INFO
General information
1-2162Y3A11
Acceleration control
This control is activated when the throttle valve is opened suddenly. If the engine speed increases
more than the specified figures, the control of the ignition timing transfers to the acceleration map.
Thereafter, the control of the ignition timing transfers gradually to the control map before accelera-
tion. If it was under warm-up control, the timing transfers to the warm-up control map, and if it was
under normal control, the timing...

62Y3A111-22
1
2
3
4
5
6
7
8
I
Power trim and tilt
The newly designed power trim and tilt consists of an up-main valve, a down-main valve, an up-
relief valve, a single cylinder, and a single ram, which control both trim and tilt functions.
The power trim and tilt cylinder has been integrated with the gear pump housing, the reservoir tank,
and the power trim and tilt motor in order to achieve a smaller and more compact unit.
Hydraulic system diagram
1Power trim and tilt cylinder
2Ram
3Reservoir
4Manual...

GEN 
INFO
General information
1-2362Y3A11
Power trim and tilt components
1Cylinder
2Ram
3Check valve
4Down-main valve
5Down-relief valve
6Motor
7Gear pump
8Up-main valve
9Reservoir
0Manual valveAUp-relief valve
BUp-shuttle piston
CDown-shuffle piston
DTrim cylinder base
EFree piston
FTilt piston
2
3
546
7
8
9
0
A
B 9 C
D E F 1
S62Y1380 

62Y3A111-24
1
2
3
4
5
6
7
8
I
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...

GEN 
INFO
General information
1-2562Y3A11
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...