I have a 1998 5.0 GI Volvo Penta engine. The boat had sat idle for over 6 months with ethanol fuel in it. This made a number of problems. However after changing the low and high fuel pumps, emptying the fuel tank and replacing the gas with ethanol free gasoline, changing the fuel filter and pump relays and rebuilding the float mechanism in the fuel reservoir the engine runs fine. I have been testing to max throttle 4600-4800 rpm with no problems and great performance. However, if I run the engine hard and then shut it down, it won?t start again. When cranking I can hear several cylinder fire, but it never revs up. Occasionally it will backfire. It is fine again once it cools down. Any thoughts would be appreciated.