mercury 220 hp laser efi

[lifloorguy]

ok heres the problem i bought a 79 checkmate. 220 hp efi. had water in tank took the tank out replaced fuel/water filter. actually mechanic did. ran fine for a day or so. now when i start it runs for a second and stalls some smoke blows. only stalls when idle or when i put it in gear.this happen sometimes but more often. runs fine at 30-50 mph. if i am idling down the canal it putters then dies when i put it in neutral. any suggestions?