If you aint found the problem yet look for the high speed (air) jet on the outside of the carb. I was missing the low speed jet and mine did right the opposite. At low speed it sounded like it was gonna choke down. (Mine's a 2 cyclinder 50 hp and sounded like it was running off 1 cyclinder.) At high speed it did fine. On mine, the (air) jets are on the side of the carbs. I was looking and seen what looked like a screw missing on the top/side portion of the carb. The one under it had a brass like bushing in the screw hole so I knew then what was missing. Good luck straightening it out.
Health nuts are going to feel stupid someday, lying in hospitals dying of nothing.