2016 Merc 150hp outboard intermittent rough running issue

[nasdaqsam]

As stated, every once in a while, the motor will run like it is in guardian mode. All I have to do is bring it back to idle and start out again and it stops for a while. It doesn't matter if I am just barely moving or on plane it happens either way.

I don't think it is water in the gas because it will do it until I idle it down and go back up regardless of how long that is. I only use ethanol free gas and add ethanol treatment.

The tach does on occasion show overrevving not when the motor is acting up but occasionally. I just have to tap it and it goes back to whatever RPM I am running. My mechanic feels the tach could be the issue, but I thought the tach just showed the motor rpm not the motor relying on it to run properly. ???

I read on here it could be the coils it's a known issue. Is there any way to test this? I don't want to just throw parts at it.

Thank you in advance for any assistance you may offer. I do not get online a lot so might be a little bit before I can answer questions or get back to anyone.

 

[alldodge]

My mechanic feels the tach could be the issue, but I thought the tach just showed the motor rpm not the motor relying on it to run properly. ???

Your Mech could be right. The Tach gets it's info from the ignition system and if it starts shorting out or drawing more current this will effect the firing of the plugs.

Could disconnect the gray wire from the coil to see if it problem stops

 

[nasdaqsam]

I can't unhook just the Gray wire its a whole plug in connection. I disconnected it the connector and will try it to see if that's it. Might take a bit as like I said it's intermittent.

Thank you