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NOTE: When trouble-shooting power heads of 4-cycle outboard motors, follow procedures outlined for inboard engines.
START ALL MAJOR DIAGNOSIS WITH A COMPRESSION TEST. DO NOT RUN MOTOR OUT OF WATER. MOTOR REACTION 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 bottom.
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 piston.
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 bracket.
L Improper tension adjustment on dual cable systems. |
