I noticed that the motor was sputtering a bit at high RPM while in the water. I rebuilt the carbs last week hoping that it would fix the issue. After starting it takes about 10-15 seconds for water to circulate through the engine and then it will die within 30 seconds to a minute. It is idling great and sounds like everything is fine and then a rough, slower idle and then kaput! I have been trying to tweak the idle screw to see if that is part of the issue with no success. I just cleaned the plugs last week and took a look at them again yesterday and they are filthy (picture attached). Any help with this would be greatly appreciated!!