If he switched carbs, that wouldn't explain only #2 fouling. But then agin that plug doesn't look that bad, I think you might be on the right track but not flooding if it was flooding the cyc, it wouldn't be black, black indicates it firing and burning, if it was flooding it would be clean and wet dripping gas.
Maybe. If the cabs were switched and there is an air leak in the cylinder then the same result will happen with any carb that is put in place. If there is a gasket between the head and carb and the leak is there then the carb may be giving too much fuel because of a lack of back pressure. If the leak is internal then the engine will be starved for air on the compression stroke because the air will be lost through the leak area. The engine will still fire but will be sluggish.
Have you done a leak down test on the engine? Specifically that one cylinder.
Sorry Duck I'm going to have to disagree with you. I'm not sure what you mean about a gasket between the carb and head. There are multiple gasket between the carb and head IE head gasket, intake seal (not a gasket but a gel) reed gasket, carb gasket etc etc.
He still hasn't answered my questions on year, which would answer my other questions. It's going to be very different diagnosis if it a 60 degree or 90 degree motor, as they operate differently. Also if it is using a VRO system vs a diaphragm pump will make a difference.
My Dad became OMC certified in 1978 and owned his dealership since 1983 which was strictly OMC till 1994 when he also became Mercury authorized he went to school every year until OMC folded, he was a master OMC tech since 1985, my uncle also worked there for 15 years and was an OMC master tech I asked both of them about your theory and either I'm explaining it wrong because I'm not sure what you are saying or it just doesn't add up.
I do believe his motor is an 80's model and believe me when I tell you my dad knows his crap on those engine. He use to have 70% of the parts catalog memorized.
