Engine Runs Rough, Misses, Or Backfires; Poor Performance; Excessive Engine Temperature; Insufficient Engine Temperature - Mercury 4.3 MPI SeaCore Operation & Maintenance Manual

Engine Runs Rough, Misses, or Backfires

Possible Cause
Clogged fuel filter.
Stale or contaminated fuel.
Kinked or clogged fuel line or fuel tank vent line.
Flame arrestor dirty.
Faulty ignition system component.
Idle speed too low.
EFI system fault.

Poor Performance

Possible Cause
Throttle not fully open.
Damaged or improper propeller.
Excessive bilge water.
Boat overloaded or load improperly distributed.
Flame arrestor dirty.
Boat bottom fouled or damaged.
Ignition problem.
Engine overheating.
EFI system fault.

Excessive Engine Temperature

Water inlet or seacock closed.
Drive belt loose or in poor condition.
Seawater pickups or sea strainer obstructed.
Faulty thermostat.
Coolant level (if equipped) low in closed cooling section.
Heat exchanger or fluid cooler plugged with foreign material.
Loss of pressure in closed cooling section.
Faulty seawater pickup pump.
Seawater discharge restricted or plugged.

Insufficient Engine Temperature

Faulty thermostat.
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Possible Cause
Possible Cause
Replace filter.
Drain fuel tank. Fill with fresh fuel.
Replace kinked lines or blow out lines with compressed air to remove
obstruction.
Clean the flame arrestor.
Service ignition system.
Have EFI system checked by an authorized Mercury MerCruiser dealer.
Have EFI system checked by an authorized Mercury MerCruiser dealer.
Inspect the throttle cable and linkages for proper operation.
Replace the propeller.
Drain and check for cause of entry.
Reduce load or redistribute load more evenly.
Clean the flame arrestor.
Clean or repair as necessary.
See Engine Runs Rough, Misses, or Backfires.
See Excessive Engine Temperature.
Have EFI system checked by an authorized Mercury MerCruiser dealer.
Open.
Replace or adjust belt.
Remove obstruction.
Replace.
Check for cause of low coolant level and repair. Fill system
with proper coolant solution.
Clean heat exchanger, engine oil cooler, and transmission oil
cooler (if equipped).
Check for leaks. Clean, inspect, and test pressure cap.
Repair.
Clean exhaust elbows.
Section 6 - Troubleshooting
Remedy
Remedy
Remedy
Remedy
Replace.
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