Purchasing Boat Gas

[Greene's Basin Girl]

I have always purchased gas for my Seadoo at gas stations- not marina's. We just purchased a new pontoon boat with a new 150hp Honda engine on it. Will it hurt the engine if I purchase the gas off water? I know the marina's say that they have extra ingredients in their gas, but I wonder if it makes a difference? I would like to save some money on the gas. Our new pontoon boat has a 50 gallon tank. We travel all over the lake so we are spending many $$$$$.