I just spoke to the Mercury mechanic when I dropped off my 9.9 and the tank. After explaining what was going on, she said well, the first thing is the tank you are using. Its a small 4 gallon EPA certified tank. She said that these tanks do not relieve pressure until it hits 5lbs inside. She said it forces too much fuel into the engine therefore flooding the engine. She siad the first thing she is gonna do is install a pressure relief valve in the tank!