Engine had overvoltage code 15 times over 1-2 month period(57volt alarm). Engine trouble light would only occurr between 1k-2k RPM, Turning off motor and turning on cleared alarm, engine would resume operating properly until next alarm. Seemed to occur more on load, going slow underload bucking the tide, again always at just above idle while motoring in harbor no wake zone. Never occured at speed.
Dealer put laptop on it a couple of times confirmed always the same code, diagnosed as bad EMM, voltage regulator problem. Replaced EMM with a new factory EMM downloaded with my supplied old EMM data. With new EMM engine ran for 45 minutes and cut off. Now at dealer with no codes showing? They are having trouble diagnosing 2 weeks at dealer?, did I get a bad EMM?
Because we are not there to see and test your motor, we can only offer suggestions. Your dealer technician should be able to diagnose things for you and repair what is needed.
One thing that is often overlooked is the blue capacitor. Many times a system voltage problem is caused by loose or corroded connections under the rubber boot, or a leaking or noisy capacitor when shaken. There is also a test for the operation listed in the service manual.
"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.