Mercury 150 EFI Service Manual page 80

Symptom
3. Engine idle is rough
4. Engine idles fast (rpm
>700) or surges
5. Engine runs rough below
3000 rpm
6. Engine runs rough above
3000 rpm
90-883728 JULY 2001
Cause
3.1 Fouled spark plug
3.2 Failed fuel injector
3.3 Bad coil/weak spark
3.4 Flywheel misaligned during
installation
4.1 Fuel leak
4.2 Improper set-up
5.1 Fouled spark plug
5.2 Throttle misadjusted
5.3 Bad coil/weak spark
5.4 TPS malfunction
6.1 Fouled spark plug
6.2 Speed Reduction
6.4 TPS malfunction
Action
Replace spark plug: if carbon
bridges electrode gap or if it is
completely black. If it is not firing
and is wet with fuel.
Note: If spark plug is grey or com-
pletely black with aluminum specs,
this indicates a scuffed piston.
Refer to specifications for ohm
test.
Refer to specifications for ohm
test.
Remove flywheel and inspect.
Check for fuel entering induction
manifold.
Fuel pump diaphragm leaking and/
or Vapor Separator flooding over.
Check throttle cable & cam roller
adjustment.
See 3.1
Check throttle cam setup on induc-
tion manifold. Inspect linkage and
roller.
If throttle plate stop screws have
been tampered with, contact Mer-
cury Marine Service Department
for correct adjustment procedures.
See 3.3
See 2.2
See 3.1
See 7
See 2.2
IGNITION
Page 2A-23