Hello experts, I need your suggestions again.
I have a 2006 mercury optimax 115hp, serial 1B255833 i've owned since new.
This motor has run flawlessly all the time, and I have to admit maintenance has been ok but not what should have been to be perfect, but I started to put more love in it recently.
It recently started idling a bit rougher than normal, and when I took it to the water to do a trailer swap I decided to do a quick run to get fuel flowing thru, but it had very little power, and could not get over 2500 RPM. I did not get any smartcraft alerts or recorded any faults.
I began diagnosing by removing all the gas from the tank and adding new non-ethanol gas, emptied the VST, changed the VST filter, rebuilt the diaphragm pump, cleaned the VST (thing looked brand new inside), tested fuel pumps and all the normal fuel maintenance. I pulled the plugs to replace and noticed that the bottom plug electrode was completely covered in carbon, so most likely that's the reason for the loss of power as I doubt there was any spark there. Later I swapped the plugs and put new NGK plugs in it.
I figured the injectors could use service and a bad spray pattern could be the reason for the high carbon in the plug. Pulled the injectors and had them serviced by a local shop, and cleaned my fuel rail and hoses but barely any dirt came out, everything looked really clean.
Put everything back together and had the motor running up to temperature with the clean injectors. Idle is much better with a slight vibration which I think is normal but after about 20 minutes of running time I decided to check on the plugs and while top and mid looked new, the bottom plug looked like carbon is already building there.
I don't know if this is normal, or not. for the time being I swapped mid and bottom plugs to see if the new plug on the bottom begins building carbon too.
While I do my tests I would love to hear suggestions from the experts if there is anything I should be looking into or if I'm overthinking too much and this is normal.