Gone Outdoors

How to Use Engine Tuner for a Johnson Outboard

by Will Charpentier

Engine Tuner is a spray chemical made by Evinrude/Johnson, used to remove carbon deposits from outboard motor pistons during a tune up. Excessive carbon build up makes a piston's rings stick to the walls of the cylinder, resulting in blow-by or high oil consumption. The manufacturer recommends spraying Engine Tuner into the motor with each fuel fill up as a prophylactic measure; keep the carbon build-up under control incrementally and you will not need to resort to more excessive measures.

Plug a garden hose into the motor's flushing system whether that system uses a direct connection or a flushing attachment. Turn the water on full force to supply cooling water to the motor. Start the motor and run it at normal idle until it reaches its normal operating temperature.

Set the engine to fast-idle by pulling the fast-idle lever upward. Spray the contents of the can of Engine Tuner into the throat of the carburetor. For most engines, a fast-idle of around 1,200 rpm will warm the motor sufficiently to heat the carbon entrapped in the Engine Tuner, and expel it from the exhaust.

Shut the engine down. Disconnect the black, negative battery cable. Remove the spark plugs wires by twisting them, then pulling each wire away from the spark plug. Remove the spark plugs one at a time, with a spark plug wrench, so as to not return the spark plug to the wrong bore. Lay the engine on its side and peer through the spark plug holes as you slowly turn the motor over by hand.

Turn the flywheel by hand, watching the piston position. When the piston position is such that the valves are closed, spray enough Engine Tuner into the cylinder to cover the top of the piston. Reinstall the spark plug and tighten it to the torque specified by the manufacturer, but do not reconnect the spark plug wire. Move to the next cylinder and repeat.

Wait 2 hours, then turn the flywheel through at least three full revolutions by hand, to remove the cleaner. Reconnect the spark plug wires. Start the engine and allow it to reach its normal operating temperature before shutting it off.

Items you will need
  • Garden hose
  • Flushing attachment
  • Engine Tuner
  • Spark plug wrench
  • Torque wrench


  • "Johnson Repair Manual 2.5 to 250 HP Models, 2002-2007"; Seloc Marine; 2007

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