Supplying your outboard with fresh and clean gasoline will prevent having any injector problems.
To help things stay that way, be sure to have a boat mounted water-separator filter along with the engine filter. Always use a fuel stabilizer such as Evinrude 2+4 Fuel Conditioner if the boat is used infrequently and in a stronger concentration (per directions) before winterizing the motor.
When the fuel tank is kept close to full, there is less room for condensation to form on the inside tank walls which can combine with the ethanol in the gasoline. When moisture and ethanol mix, they drop out of the gasoline and form a layer of water and concetrated alcohol at the bottom of the tank. This is what corrodes metal parts, rots the rubber fuel lines, and forms deposits inside the fuel sytem. It also causes poor running and sometimes expensive repair problems.
"There is never just one thing wrong with a boat";
-- Travis McGee, main character in a book series by John D. McDonald
The factory recommends that a properly trained technician service your Johnson or Evinrude outboard motor. Should you elect to perform repairs yourself, use caution, common sense, and observe safety procedures in the vicinity of flammable liquids, around moving parts, near high-temperature components, and working with electrical or ignition systems.
The information offered here is only general in nature and should not be construed as complete factory approved procedures, techniques, or specifications. Always use the proper service manual for your motor, up-to-date service literature, the correct tools, and have an understanding of how to proceed with troubleshooting and repair methods. If you are unsure or uncomfortable with a procedure, a situation, or a technique, enlist the services of a factory trained technician.