Engine Speed Control System - Yamaha F150B Service Manual

TECH
FEA

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
Description
Name
Overheat Detects the
control overheat event
and controls the
engine speed.
Low oil Detects the low
pressure oil pressure and
control controls the
engine speed.
D.E.S. Detects the
Control activation of
D.E.S. and
controls the
engine speed.
Shift Detects the
cutout shift-cutout
control control
activation and
controls the
engine speed.
Engine Cancels the fuel injection control and the ignition control at all cylinders.
shut-off
switch ON
Over- Controls the
revolution engine speed
control when an over-
revolution
condition is
detected.
2-13
Technical features and description
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 is identified when it drops to 250.0 kPa (2.50 kgf/
2
cm ) 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 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.
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
Less than 400 r/min
400–729 r/min
730–2000 r/min
Over 2001 r/min or
more
Engine ECM controls the engine speed by carrying out the fuel
injection stop control over 5750 r/min.
Engine speed
Less 5750 r/min
5750–5852 r/min
5852–6102 r/min
6102 r/min or more
Engine condition
ON
No misfire control
Retards ignition tim-
ing
Misfires the #1 and
#4 cylinders, and
then retards igni-
tion timing
No misfire control
Fuel injection stop
None
#1 and #4
#1, #3, and #4
All cylinders
OFF
No misfire control
No misfire control
No misfire control
No misfire control