Last season I was helpin my dad fix his boat it wouldn't run right. We put a new diaphram, cleaned the carbs. ajusted the carbs for a smooth running engine. Put new gas in it as well. He took it out on a lake and it ran fine. The next time we took it out it wanted to go but it sounded as if it was misfiring. It would take off then no power at all spitting and sputtering along. This was on full throttle. Then he backed off a little to wich the problem was somewhat better so I am thinking that it may be a plug that is fouling out any ideas on what this could actually be? To note he puts a fuel additive in his engine to stablize the fuel. I think that might be it as well the spark might be running to hot. We are looking to have it fix for a fathers day gift.