My 35 horse Mercury seems to be losing it's prime. When it sets for 20-30 minutes after running, It won't restart unless I hit the priming bulb 2-3 times. I have no fuel leaks and the fuel bulb is brand new. Could this be a bad float in the carb. causing this? My brothers Merc. starts right up after setting an hour without re-priming. I've also noticed if you pump it to much it floods.