Volvo Penta 350 I/O with Carburetor/Fuel problem?

I have a 97 Four Winns Volvo 5.7GL. Have a Rebuilt carburetor, new plugs, new wires, new fuel filter. Runs great on LAND and at IDLE. As soon as I put it in the water, it stalls and wont go. Seems like too much air or not enough/too much gas. Carb was set to FAST idle at 800 rpm, I believe and Load tested. I had half a tank of gas from Last year with Stabil in it... and just filled tank with PREMIUM Gas. In order to start it on water, once I have idled out, I have to hold close the erfly (which is by now WIDE OPEN) and then as soon as she starts, she runs for about a minute and then starts to stall or if I give it gas, then the same thing happens. I had this problem last year as well and was advised to get the Carb rebuilt which I did. Not sure where to go from here? Is this an electric choke issue (this is brand new as well) or a carb related problem? I thought maybe GAS as we have ethanol blend, but a Mechanic said, just put premium in it and you wont have a problem.