Update on 2014 40hp four stroke. It has the G3 ecm and can't be reflashed, unless there is a update , so travel to mercury dealer (service manager says yes bring in we'll reflash , on the phone) tech. tells me he can't reflash. But also tells me that G3 ecm doesn't go into guardian mode. Manual for 2014 with that serial # is when they were changing to single plug ecm from 2 plug ecm. So G3 ecm just reduces power at 10% intervals and doesn't , reduce power to 2500 rpm with solid alarm. Tech. said motor can run to 210 ° before ecm cuts motor back to idle. Ecm sends 5 volts to all sensors, so ect,ict,map,mat, an tps. Are resistance sensors. So as dockside said ✔ all pins and connections. Did that, now remember this is a 2014 that sat 3 years indoor storage . no corrosion , motor looks brand new. It has 62 hrs. Imo it's going to be ecm. But I can't see buying a $800 ecm to find out if that's problem. These motors are unbelivably hard to diagnose. It's getting to the point of automotive , were u just trash and buy new.
The mercury tech told me he has 4 motors in shop , after 20 yrs. he can't figure out.