Spark plugs create a small explosion inside the motor when combined with fuel, thus engaging the pistons on your outboard motor. A spark plug must be gapped correctly in order to leave enough room for the spark to ignite on the tip of the plug. Consulting your outboard motor's owner's manual will tell you the correct gap size specific to your motor. The spark plugs must be securely tightened with the help of a torque wrench.
Remove the spark plug leads from each spark plug on your outboard motor. The spark plug leads cap the spark plug and connect to a wire that goes from the plug to the motor. Pull the cowling from the spark plug, using your hand.
Consult your outboard's manual to determine the gap size for your motor's spark plug. Use a gap tool to pry the spark plug gap to the correct measurement on the tool. Slip the gap tool between the spark plug and the igniter and pry the tip up until it fits within the specific measurement. Remove the gap tool from the spark plug.
Insert the spark plug into the outboard motor's spark plug slot. Use a torque wrench to tighten the spark plug clockwise at a measurement of 20 foot-pounds of torque to secure it to the motor.
Place the spark plug lead onto the end of the spark plug to connect the spark plug to the outboard motor.
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