I took her out today for the first time this season. I have a 5.0 Merc with a 2 bbl carb which was rebuilt at the beginning of the 2017 season due to ethanol issues. I always use Startron at every fill up and for the winter storage. Today at first she ran smooth. Got up on plane and ran flawless at 3400 Rpm. I even brought it up to 3800 with no problems. As I was pulling back on the throttle when I got under 3000 she started to bog down. The rpm's were fluctuating between 2500 and 2800. When I tried to go higher it bogged down. I pulled it down to around 1000RPM and it was still fluctuating. At one point it did stall out on me. I got it started. As I gave it throttle it would bog down but then at one point it ran smooth and ran fine again at 3400. I pulled back again and the same thing happened. I got it down to the point where it would idle and I got it back to the marina. Could I have water in the gas? I was going to pull the fuel water separator off and empty it out and see if there is water in it. Or could I be having some sort of carb issue again? Any input would be greatly appreciated.