MOTC Manual - edited

Remember! Work from simple to complex. The priority for troubleshooting system
failures is eliminating the simplest possible causes for a problem before putting time and
effort into more complex possibilities.
Whenever working near moving parts of a motor, make sure power to the motor
(master switch) is off.
The following list identifies possible causes for common system failures:
1. Engine hard to start or will not start (More likely not to start than to quit while
running)
Empty gas tank
Fuel quality bad (water in fuel)
Primer bulb not firm
Gas tank air vent closed
Fuel valve closed
Fuel line kinked, clogged, cracked, or not attached
Fuel filter clogged
Water or dirt in system
Motor must be choked
Carburetor adjusted too lean
Ignition timing off
Choke linkage bent or out of adjustment
Ethanol-related problems (Consult engine manufacturer)
Engine compartment hot causing vapor-lock (fuel-injected inboards)
2. Low speed miss
Too much or too little oil
Ignition timing
Carburetor
Weak coil
Loose or broken ignition wires
3. High speed miss
Bad spark plugs
Loose or broken ignition wires
Weak coil
Water in fuel
4. Runs well for a while and then quits
Weeds or other debris on prop
Insufficient cooling water
Carburetor, fuel pump, filters or screens dirty
Lower unit bind (lack of lube, or bent)
DOI – Motorboat Operator Certification Course Chapter 2 – 16