How to Start a Flooded Outboard Motor

Updated July 20, 2017

A flooded outboard motor can spoil the enjoyment of a day of boating or fishing. A flooded engine has excessive fuel in the cylinder(s), which fouls the spark plugs, creates an overly rich mixture of fuel and air inside the engine, and causes difficult or impossible starting. Following the simple steps below will introduce extra air into the outboard motor's cylinder(s), diluting and helping evaporate the excess fuel, and allowing the motor to start and the day's activities to continue.

Raise the warm-up or fast-idle lever as far as it goes. This will allow more air to enter the motor and help clear the flooded condition.

Crank the motor for eight to 10 seconds or pull the starter rope several times. Do not apply the choke or pump the primer bulb, as doing so will cause more fuel to enter the cylinders and make the flooded condition worse.

Repeat Step 2 until the motor starts, allowing the starter a break for four or five seconds between attempts.

Leave the warm-up/fast-idle lever raised until the motor runs smoothly, once the motor starts. Be careful not to rev the engine too high. Slowly lower the lever until the motor is idling at a normal idle speed.

Remove the spark plug(s) and wipe the tip(s) dry using a clean, dry rag if the motor still does not start. Attach the spark plug wires to the grounds provided or move them away from the spark plug holes. Crank the motor over several times with the spark plugs out to help clear excess fuel from the cylinders.

Reinstall the spark plugs and connect the spark plug wires. Return to Step 1.


If the flooded condition is severe enough to require cranking the engine with the spark plugs removed, be aware that the fuel mixture which is blown out of the spark plug holes is highly flammable. Extinguish any open flames or smoking materials in the vicinity and place the spark plug wires out of the way to avoid any sparks.

Things You'll Need

  • Spark plug socket (optional)
  • Ratchet or pull handle (optional)
  • Dry rag (optional)
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About the Author

Herb Holloway began writing in 1989. His master's thesis was published in the "American Journal of Agricultural Economics." Holloway has written numerous research publications and publishes a quarterly newsletter for the Southeastern Louisiana University Business Research Center. He holds a Master of Science in agricultural and resource economics from North Carolina State University.