1991 Johnson 150 GT

My 1991 Johnson 150 GT runs great on plane but misses and stalls bad at slow speeds. It starts good, has new plugs,new gas with Seafoam. Smokes bad at slow speeds. Any suggestions?

Check the enrichment valve, it could be leaking by fuel. Idle circuits on carbs dirty. Vro pump fuel pressure side at idle causing motor to get too much oil, Needle and seat leaking on one carb. Just some of the possible causes.