I have air bubbling up from the bottom of motor at idle. Also more exhaust air seems to be coming from exhaust port on back of engine now. See video...
Ask your dealer if the muffer needs to be updated to the latest one.
There is a possibility of internal muffler damage if the engine has had overheating alarms or sometimes if the engine is overpropped and lugging for long periods of time.
"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.