Rebuilt the carbs on my 1971 Johnson 50HP this weekend and need some pointers on how to go about adjusting them. Engine starts easy, runs great, but I think it may be burning a little rich. I'm getting a lot of smoke and black soot. The repair manual I have is rather generic for several generations of motors that span from 1971 to 1989 and I couldn't find any step-by-step tips. Can anyone help?