Look on the front of your gearcase above the bullet area and you will see a small black hose and an 'L' shaped fitting. Carefully remove the hose and blow through the fitting and air should come out of a small hole on the very front of the bullet part of the gearcase. If the hole is plugged with mud, sand, etc. then it would be best to see a dealer about getting it cleaned out. Do not use a drill !
"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.