15 hp johnson choke/throttle problems

1982 15 HP Johnson had carb rebuilt (not by me) 3 years ago.It sat 2 yrs until I purchased last year. Carb was cleaned ,new plugs put in, & bought new tank. Went "downhill" more with every use. As I opened it up, I discovered that I had to pull out choke to get it to maintain speed. When I would throttle down it then would die. I tried Sea Foam in tank, that marginally helped. Just got worse with each use. Ran dry B/4 storage. I sprayed carb,installed new plugs (old ones slightly fouled), new gas w/sea foam. Put boat in yesterday. Did "OK", but still have to pull out choke to get it to stay buzzing. Had to set mix dials to rich setting. Does my carb need pulled and soaked? Or is something else going on here?