[THEFERMANATOR]

Flames behind the butterfly doesn't sound good, that sounds like a broken reed and some other issues. An extreme lean condition could cause it to let some flames up into the crankcase, but you shouldn't be able to see them through the butterfly. The issues you describe though in your posts sounds to me like a normal carbed 2 smoker running though. They all smoke some and load up and cough a bit, this is one of the big reasons why people get kicker motors for trolling. The big outboards just don't do well at low RPM's. I would say cleaning the carbs couldn't hurt, and get you a manual that walks you through setting the timing and linkage and see if that helps it.