MerCruiser 350 Magnum MPI, Operation & Maintenance Manual

Page: 58 / 76

56
Possible Cause Remedy Trouble
Engine runs
rough, misses
and/or backfires •
Faulty fuel pump
•
Idle speed too low (if engine is
rough at idle)
•
Faulty ignition system component
•
Clogged fuel filters
•
Check sight tube. Have your dealer replace
pump, if fuel is present.
•
Check idle speed and adjust, if necessary.
•
Service ignition system
•
Replace filters.
Poor performance
•
Contaminated fuel
•
Kinked or clogged fuel line or fuel
tank vent line
•
Flame arrestor plugged with
foreign material.
•
Throttle not fully open
•
Damaged or improper propeller
•
Excessive bilge water
•
Boat overloaded or load improp-
erly distributed
•
Boat bottom fouled or damaged
•
Flame arrestor dirty
•
Inspect fuel for water or other contaminants.
If contaminated, drain tank and flush. Fill with
fresh fuel.
•
Replace line if kinked. Blow out line with
compressed air to remove obstruction.
•
Clean flame arrestor.
•
Inspect cable and linkages for binding, ob-
struction or loose fasteners.
•
Replace.
•
Drain and check for cause of entry.
•
Reduce load or redistribute load more evenly.
•
Clean or repair as necessary.
•
Clean flame arrestor.
Excessive engine
temperature
•
Engine overheating
•
Ignition or EFI System fault
•
See “Excessive engine temperature”.
•
Refer to “Engine runs rough, misses and/or
backfires”.
•
Water inlet valve closed (if so
equipped)
•
Alternator drive belt loose, broken
or in poor condition
•
Seawater pickup pump drive belt
loose, broken or in poor condition.
•
Water pickup obstructed
•
Kinked, collapsed or broken hose
•
Faulty thermostat
•
Open valve COMPLETELY.
•
Replace and/or adjust belt.
•
Replace and/or adjust belt.
•
Remove obstruction.
•
Straighten or replace hose.
•
Replace.
•
Transmission fluid cooler and/or
engine oil cooler plugged with
foreign material
•
Disconnect hoses from coolers and flush out with
a water hose in direction opposite normal water
flow.
(continued next page)
•
EFI System Fault
•
Have EFI System checked by an Authorized
MerCruiser Dealer.