does not stumble at high speeds just takes awhile to get there, can push the throttle all the way down and does not accelerate takes a min to get to speed . new plugs last fall with only had the boat out twice with new plugs, new gas about a week ago. checked the wires they all look good. the motor is a 1986 and the prop is brand new a year ago. i had problems a couple months ago with gas coming out of the vent jet so i took the carbs off cleaned them and the boat ran at full speed put would not run at trolling speed so took them back off to make sure i didnt miss anything put them back on and now idles fine runs at low speed good but just wont jump to full throttle right. thanks guys