Troubleshooting a New or Rebuilt Outboard Engine

George Van Parys

Mar 1, 2000
RO Number



1. Manual starter rope pulls out, but pawls do not engage.
A. Friction spring bent or burred.
B. Excess grease on pawls or spring.
(too heavy of a grease used?)
C. Pawls bent or burred.

2. Starter rope does not return.
A. Recoil spring broken or binding.
(too heavy of a grease used?)
B. Starter housing bent.
C. Loose or missing parts.

3. Clattering manual starter.
A. Friction spring bent or burred.
B. Starter housing bent.
C. Excess grease on pawls or spring.
D. Dry starter spindle.
E. Just plum worn out...

4. Electric starter inoperative.
A, Loose or corroded connections or ground.
B. Starting circuit safety switch open, or out of adjustment.
C. Improper capacity or weak battery or corroded battery terminals
D. Faulty starter solenoid.
E. Moisture in electric starter motor.
F. Broken or worn brushes in starter motor.
G. Faulty fields.
H. Faulty armature.
I. Broken wire in harness or connector
J. Faulty starter key, push button or safety switch.
K. Worn or frayed insulation.

5. Electric starter does not engage but solenoid clicks.
A. Loose or corroded connections or ground.
B. Weak battery.
C. Faulty starter solenoid.
D. Broken wire in electric harness.
E. Loose or stripped post on starter motor.
F. See steps in number 4.
G. Bendix shaft rusted or bendix clutch broken

6. Hard to start or won't start.
A. Empty gas tank.
B. Gas tank air vent not open.
C. Fuel lines kinked or severely pinched.
D. Water or dirt in fuel system
E. Clogged fuel filter or screens.
F. Motor not being choked to start.
G. Engine not primed -- pump primer system.
H. Carburetor adjustments too lean (not allowing enough fuel to
start engine).
I. Timing and synchronizing out of adjustment.
J. Manual choke linkage bent -- auto choke out of adjustment.
K. Spark plugs improperly gapped, dirty or broken.
L. Fuel tank primer inoperative (pressurized system).
M. Ignition points improperly gapped, burned or dirty or triggering
(CD) system inoperative.
N. Loose, broken wire or frayed insulation in electrical system.
O. Reed valves not seating or stuck shut.
P. Weak coil or condenser.
Q. Faulty gaskets.
R. Cracked distributor cap or rotor or shorted rotor.
S. Loose fuel connector.
T. Amplifier (CD) inoperative.
U. Poor engine or ignition ground.
V. Faulty ignition or safety switch.
W. Low cranking speed.
X. Low voltage to ignition, when cranking.

7. Low speed miss or motor won't idle smoothly and slowly enough.
A. Improper fuel/oil mixture.
(very old gas?)
B. Timing and synchronizing out of adjustment.
(linkage fell off?)
C. Carburetor idle adjustment (mixture lean or rich).
D. Ignition points improper (gap, worn or fouled) or
triggering (CD) system inoperative.
E. Weak coil or condenser.
(only way to know for sure... Replace it)
F. Loose or broken ignition wires.
G. Loose or worn magneto plate.
H. Spark plugs (improper gap or dirty incorrect plug).
(don't waste time try a new set)
I. Head gasket, reed plate gasket (blown or leaking).
J. Reed valve standing open or stuck shut.
K. Plugged crankcase bleeder, check valves, or lines.
L. Leaking crankcase halves.
M. Leaking crankcase seals (top or bottom).
N. Exhaust gases returning thru intake manifold.
(cowling seals missing or damaged)
O. Poor distributor ground.
(look for a grounding wire or add one)
P. Cracked or shorted distributor cap or rotor.
Q. Fuel pump diaphragm punctured.
(check spark plugs, usually one will be running very rich)
R. Accessory tachometer shorted or not compatible
with ignition system.
S. Faulty ignition or safety switch.

8. High speed miss or intermittent spark.
A. Spark plugs improperly gapped or dirty.
B. Loose, leaking or broken ignition wires.
C. Breaker points (improper gap or dirty. worn cam or cam
follower) or triggering (CD) system faulty.
D. Weak coil or condenser
E. Water in fuel.
F. Leaking head gasket or exhaust cover gasket.
G. Incorrect spark plug
H. Engine improperly timed.
I. Carbon or fouled combustion chambers.
J. Magneto, distributor, or CD triggering system poorly grounded.
K. Distributor oiler wick bad.
(points are hopping)
L. Accessory tachometer shorted or not compatible with
ignition system.
M. Faulty ignition or safety switch.

9. Coughs, spits, slows.
A. Idle or high speed needles set too lean.
B. Carburetor not synchronized.
C. Leaking gaskets in induction system.
D. Obstructed fuel passages.
E. Float level set too low.
F. Improperly seated or broken reeds.
G. Fuel pump pressure line ruptured.
H. Fuel pump (punctured diaphragm), check valves stuck open or
closed, fuel lines leak.
I. Poor fuel tank pressure (pressurized system).
J. Worn or leaking fuel connector.

10. Vibrates excessively or runs rough and smokes.
A. Idle or high speed needles set too rich.
B. Too much oil mixed with gas.
C. Carburetor not synchronized with ignition properly.
D. Choke not opening properly.
E. Float level too high.
F. Air passage to carburetor obstructed.
G. Bleeder valves or passages plugged.
H. Transom bracket clamps loose on transom.
I. Prop out of balance.
J. Broken motor mount.
K. Exhaust gases getting inside motor cover.
L. Poor ignition -- see steps in number 8.
M. Motor too low in water.
(excessive exhaust back-pressure)
11. Runs well, idles well for a short period, then slows down and stops.
A. Weeds or other debris on lower unit or propeller.
B. Insufficient cooling water.
(especially probable with inline
C. Carburetor, fuel pump filter or screens dirty.
D. Bleeder valves or passages plugged.
E. Lower unit binding (lack of lubrication or bent).
F. Gas tank air vent not open.
G. Not enough oil in gas.
H. Combustion chambers and spark plugs fouled, causing pre-ignition.
I. Spark plug heat range too high or too low.
J. wrong propeller (PreIgnition).
K. Slow speed adjustment too rich or too lean.

12. Won't start, kicks back, back fires into lower unit.
A. Spark plug wires reversed.
B. Flywheel key sheared.
C. Distributor belt timing off (magneto or battery ignition).
D. Timing and synchronizing out of adjustment.
E. Reed valves not seating or broken.
F. Poor engine or distributor ground.
G. Extremely lean operation

13. No acceleration, low top RPM
A. Improper carburetor adjustments.
B. Improper timing and synchronization.
C. Spark plugs (improper gap or dirty).
D. Ignition points (improper gap or faulty).
or triggering (CD) system.
E. Faulty coil or condenser.
F. Loose, leaking or broken ignition wires.
G. Reed Valves not properly seated or broken.
H. Blown head or exhaust cover gasket.
I. Weeds on lower unit or propeller.
J. Incorrect propeller.
K. Insufficient oil in gas.
L. Insufficient oil in lower unit.
M. Fuel restrictions.
N. Scored cylinder -- stuck rings.
O, Marine growth, hooks, rockers or change in load of boat, or flooded
P. Sticky magneto plate or distributor.
Q. Carbon build-up on piston head at deflector.
R. Marginal CD amplifier or pulse pack.

14. No acceleration, idles well but when put to full power dies down.
A. High or law speed needle set too lean.
B. Dirt or packing behind needles and seats.
C. High speed nozzle obstructed.
D. Float level too low.
E. Choke partly closed.
F. Improper timing and synchronization.
G. Fuel lines or passages obstructed.
H. Fuel filter obstructed. Fuel pump not supplying enough fuel.
I. Not enough oil in gas.
J. Breaker points improperly gapped or dirty.
K. Bent gearcase or exhaust tube.
L. Marginal CD amplifier or pulse pack.
M. Faulty spark plugs.
N. Incorrect propeller.
O. Roughness or damage on front of gearcase causing ventilation

15. Engine runs at high speed only by using hand primer.
A. Carburetor adjustments.
B. Dirt or packing behind needles and seat.
C. Fuel lines or passages obstructed.
D. Fuel line leaks.
E. Fuel pump not supplying enough fuel.
F. Float level too low.
G. Fuel filter obstructed.
H. Fuel tank or connector at fault.

16. Loss of power under heavy load.
A. Wrong propeller.
B. Weeds or other debris on lower unit or propeller.
C. Breaker points improperly gapped or dirty.
D. Stator plate loose
E. Ignition timing over advanced or late.
F. Faulty carburetion and/or faulty ignition.
G. Prop hub slips.
H. Scored cylinders or rings stuck.
I. Carbon build up on piston head at deflector.

17. Cranks over extremely easy on one or more cylinders.
A. Low compression.

1. Worn or broken rings.
2. Scored cylinder or pistons.
3. Blown head gasket.
4. Loose spark plugs.
5. Loose head bolts.
6. Crankcase halves improperly sealed.
7. Burned piston.

18. Engine won't crank over.
A. Manual start lock improperly adjusted.
B. Pistons rusted to cylinder wall.
C. Lower unit gears, prop shaft rusted or broken.
D. Broken connecting rod, crankshaft or driveshaft.
E. Coil heels binding on flywheel.
F. Engine improperly assembled.
G. Water in cylinders

19. Motor overheats.
A. Motor not deep enough in water.
B. Not enough oil in gas or improperly mixed.
C. Bad thermostat.
D. Seals or gaskets (burned, cracked or broken).
E. Impeller key not in place or broken.
F. Plugged water inlet, outlet or cavity.
G. Obstruction in water passages.
H. Broken, pinched or leaking water lines.
I. Improper ignition timing.
J. Motor not assembled properly.
K. Shorted heat light wiring.
L. Bad water pump impeller, plate, housing or seal.

20. Motor stops suddenly, freezes up.
A. No oil in gas, or no gas.
B. Insufficient cooling water.
C. No lubricant in gearcase.
D. Rusted cylinder or crankshaft.
E. Bent or broken rod, crankshaft, driveshaft, prop shaft, stuck
F. Bad water pump or plugged water passages.

21. Motor knocks excessively.
A. Too much or not enough oil in gas.
B. Worn or loose bearings, pistons, rods or wrist pins.
C. Over advanced ignition timing.
D. Carbon in combustion chambers and exhaust ports.
E. Manual starter not centered.
F. Flywheel nut loose.
G. Flywheel hitting coil heels.
H. Bent shift rod (vibrating against exhaust tube).
I. Loose assemblies, bolts or screws.
J. Broken teeth in gearcase.

22. Generator or alternator will not charge.
A. Battery condition.
B. Connections loose or dirty.
C. Drive belt loose or broken.
D. Faulty regulator or cutout relay.
E. Field fuse or fusible wire in regulator blown.
F. Generator not polarized (D. C. generators).
G. Faulty generator or alternator.
H. Worn or sticking brushes and/or slip rings.
I. Faulty rectifier diodes (alternators)
J. Faulty ammeter.
K. CD voltage regulator faulty.
L. Rectifier not grounded.
M. CD safety circuit grounded.
N. Excessive electrical load on system

23. Low generator or alternator output and a low battery.
A. High resistance at battery terminals.
B. High resistance in charging circuit.
C. Faulty ammeter.
D. Low regulator setting.
E. Faulty rectifier diodes (alternators).
F. Faulty generator or alternator.
G. Excessive electrical load on system

24. Excessive battery charging.
A. Regulator set too high.
B. Regulator contacts stuck.
C. Regulator voltage winding open.
D. Regulator improperly grounded.
E. High resistance in field coil.
F. Regulator improperly mounted.
G. Insufficient battery size (unregulated systems).
H. No water in battery

25. Excessive fuel consumption.
A. Hole in fuel pump diaphragm.
B. Deteriorated carburetor gaskets.
C. Altered or wrong fixed jets.
D. Jets improperly adjusted.
E. Carburetor casting porous.
F. Float level too high.
G. Loose distributor pulley.
H. Incorrect propeller (high rpm).
I. Boat bottom fouled
J. Lower crankcase seal deteriorated

26. Shifter dog jumps
A. Worn shifter dog or worn gear dogs.
B. Worn or bent linkage.
C. Remote control adjustment.
D. Gearcase loose or sprung.
E. Exhaust housing bent.
F. Linkage out of adjustment.
G. Rear case cover or carrier loose

27. Electric shift inoperative or slips.
A. Improper remote control installation.
B. Faulty coils.
C. Faulty springs.
D. Faulty clutch and gear.
E. Faulty bearings.
F. Wrong lubricant.
G. Loose or sprung gearcase.
H. Shorted wiring or poor connections.

28 Undesirable Steering
A. Improperly set trim tab or corroded trim tab.
B. Improper trim angle setting
C. Bent steering ram.
D. Internal corrosion in steering cable or support tube.
E. Worn helm gearing.
F. Excessive number of bends or too tight bends in steering cable.
G. Loose mounting at helm or cable output end.
H. Crushed or kinked cable.
I, Friction device at helm over tightened.
J. Leaks, dirt or low fluid level in hydraulic steerers.
K. Binding in swivel connections or motor swivel
L. Improper tension adjustment on dual cable systems.