Yamaha F150B, Service Manual

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2-13
TECH
FEA
Technical features and description
Engine speed control system
Engine speed control system on F150B reduces the engine speed in case of overheat and low oil
pressure to prevent possible engine damages.
Control
Name
Description Engine condition
Overheat
control Detects the
overheat event
and controls the
engine speed. Overheat is identified when thermoswitch is turned on and the
engine temperature is at 130 °C (266 °F) or higher.
Engine ECM stops the fuel injection to reduce the engine speed
to 2000 r/min or lower. At the same time, engine ECM activates
the alert buzzer and lights the overheat alert indicator.
Low oil
pressure
control Detects the low
oil pressure and
controls the
engine speed. Low oil pressure is identified when it drops to 250.0 kPa (2.50 kgf/
cm
2
) or lower at engine starting. It is also identified when the
pressure drops blow the specified value for each speed range.
Engine ECM stops the fuel injection to reduce the engine speed
to 2000 r/min or lower. At the same time, engine ECM activates
the alert buzzer and lights the low oil pressure alert indicator.
D.E.S.
Control Detects the
activation of
D.E.S. and
controls the
engine speed. D.E.S switch is turned on in the event of an overheat alert or a low
oil pressure alert, and the alert buzzer goes off.
Once the above event takes place, engine ECM stops the fuel
injection to reduce the engine speed to 2000 r/min or lower.
Shift
cutout
control Detects the
shift-cutout
control
activation and
controls the
engine speed. This device misfires and retards the ignition of some cylinders to
fluctuate the engine speed instantly when the engine is running
from 400–2000 r/min. This allows smooth engagement and
disengagement of the dog clutch.
When shifting, the ignition is shut off as shown in the table.
Shift cut switch ON OFF
Less than 400 r/min No misfire control No misfire control
400–729 r/min Retards ignition tim-
ing No misfire control
730–2000 r/min Misfires the #1 and
#4 cylinders, and
then retards igni-
tion timing No misfire control
Over 2001 r/min or
more No misfire control No misfire control
Engine
shut-off
switch ON Cancels the fuel injection control and the ignition control at all cylinders.
Over-
revolution
control Controls the
engine speed
when an over-
revolution
condition is
detected. Engine ECM controls the engine speed by carrying out the fuel
injection stop control over 5750 r/min.
Engine speed Fuel injection stop
Less 5750 r/min None
5750–5852 r/min #1 and #4
5852–6102 r/min #1, #3, and #4
6102 r/min or more All cylinders