When it dies does it gradually die or immediately shut down? If immed. its probably a electrical problem if slowly maybe fuel . When you go to start cold do you smell fuel or is there any in the water around the exhaust ? check fuel hose and bulb 1st.this new gas eats hose's and bulbs I'm told. Throw in some seafoam or startron from walmarts then change plugs AFTER you have ran it a little. I am definitley not a mechanic but this solved a problem similar on a friends boat. If its electrical maybe coils or ? can't help much