Evinrude E-NATION, for those dedicated to water, power, fishing and fun
Posts: 3
Registered: ‎08-10-2019

Engine Hours vs EMM Hours

Hello everyone,,

Just had my 6yr service done at a ETEC Auth Dealer and received my Engine History Report. Wanted to ask why the Eng Hours 376:24:17 is so different than the EMM Hours 120:39:4 The dealer says after he spoke with his ETEC- Support Tech they said it just happens sometimes, yet could not explain why. Said it could be that I leave my key in with it "ON". I do not do that and I have always owned this engine after purchasing it in 2012 and never had the EMM replaced. Not sure what is up here?

Posts: 79
Registered: ‎06-23-2019

Re: Engine Hours vs EMM Hours

I dont know if its the same but a riding Mower I owned would register hours when the key was left in the ignition/switch untell you removed the key.

Posts: 9,589
Registered: ‎07-14-2011

Re: Engine Hours vs EMM Hours



I have not seen it but have heard that excessive RFI from arcing plug wires, faulty sparkplugs or super worn ones with large electrode gaps, incorrect wire routing, etc. can affect the key on timer if you are positive that the EMM was not replaced.


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"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.

Posts: 951
Registered: ‎08-20-2017

Re: Engine Hours vs EMM Hours

Leaving the key on would give high EMM (key on) hours. Engine hours are actual running time. Lower EMM hours is nothing to worry about as many are not accurate.
A basic explanation. The EMM writes engine hours to memory every second. To save internal memory the EMM hours are written to memory less often so it could be like comparing two clocks where one looses a few seconds of time every hour.