IF you premix the gasoline and oil, add one pint of lubricant to 6 gallons of fuel for approximately a 50:1 ratio. Be sure the outboard oil is certified TC-W3 or better yet use the Johnson-Evinrude XD-50 oil for best results and minimum smoke.
Many dealers sell the XD-50 bulk from a barrel where you can save money by bringing in your own jug for the oil. Call around and ask.
"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.