Troubleshooting Charts; Starter Motor Will Not Crank Engine, Or Cranks Slow; Engine Will Not Start, Or Is Hard To Start; Engine Runs Rough, Misses, Or Backfires - Mercury MerCruiser Series Manual

Section 7 - Troubleshooting

Troubleshooting Charts

Starter Motor Will Not Crank Engine, or Cranks Slow

Possible Cause
Battery switch turned off
Open circuit breaker or blown fuse
Loose or dirty electrical connections or damaged wiring
Bad or discharged battery
Lanyard stop switch or E‑stop switch activated

Engine Will Not Start, or Is Hard to Start

Possible Cause
Improper starting procedure
Empty fuel tank or fuel shut‑off valve closed Fill tank or open valve.
Clogged fuel filters
Stale or contaminated fuel
Fuel line or tank vent line kinked or clogged Remove obstructions from lines.
Air in fuel system
Faulty wire connections
Electronic fuel system fault

Engine Runs Rough, Misses, or Backfires

Possible Cause
Clogged fuel or air filters
Stale or contaminated fuel
Fuel line or tank vent line kinked or clogged
Air in fuel system
Electronic fuel system faulty

Poor Performance

Possible Cause
Damaged or improper propeller
Excessive bilge water
Boat overloaded or improperly distributed Reduce load or redistribute more evenly.
Boat bottom fouled or damaged
Electronic fuel system fault

Incorrect Engine Temperature

Possible Cause
Water inlet or seacock closed
Drive belt loose or in poor condition
Seawater pickups or sea strainer obstructed
Faulty thermostat
Coolant level low in closed cooling section
Heat exchanger cores plugged with foreign material
Page 82
Turn switch on.
Check and reset circuit breaker or replace fuse.
Check all electrical connections and wires (especially battery cables).
Clean and tighten faulty connection.
Test, charge, or replace if bad.
Check lanyard stop switch, or E‑stop switch.
Read starting procedure. Be sure to allow preheat time in cold weather.
Replace fuel filters.
Drain tank. Fill with fresh fuel.
Prime fuel system.
Check wire connections.
Have the electronic fuel system checked by a Mercury Diesel authorized repair
facility.
Replace fuel or air filters.
If fuel is contaminated, drain tank. Fill with fresh fuel.
Remove obstructions from lines.
Prime fuel system.
Have electronic system checked by a Mercury Diesel authorized repair facility.
Replace propeller. See a Mercury Diesel authorized repair facility.
Drain and check for cause of entry.
Clean or repair as necessary.
Have electronic fuel system checked by a Mercury Diesel Authorized Repair
Facility.
Open.
Replace or adjust belt.
Clean strainer or remove obstruction.
Replace. See a Mercury Diesel authorized repair facility.
Check for cause of low coolant level and repair. Fill system with
proper coolant solution.
Clean heat exchanger. See a Mercury Diesel authorized repair
facility.
Remedy
Remedy
Remedy
Remedy
Remedy
90-8M0117076
eng
FEBRUARY 2018