1993 200 HP XRi EFI runs rough at idle and up to around 1800 RPM then smooths out

1993 200 HP EFI, recently replaced spark plugs (NGK), water pump, adjusted oil injection. The engine runs rough at idle, in gear it gets worse and continues until I reach 1800-1900 RPM. Then the engine will run very well. Engine has lots of power, out of the hole and top end. I have had 2 dealerships work on it and neither fixed the problem. Both gave the plugs, water pump or oil injection as the reason for running rough but I still have the problem. I did not tell the 2nd dealership that I had already had it looked at. I did not want anything they did, or what I said to sway their troubleshooting. I live in a small town, on the lake and have to drive a coupe of hours to bring my boat to a larger Mercury repair facility. i am hoping to avoid that trip. Please help. Thanks

Dirty injectors can cause this as they can cause a flooding issue at low rpm and be fine on top end. I would pull em and send to Tony Brucatto and have cleaned and flow balanced. A lot of shop can clean em but don't/cant balance the flow rates.