Reply To: 1953(54?) evinrude big twin 25hp carb

[foot_doctor]

I’m wondering if the carb with the full butterfly was used in competition. When I raced, all of the Stock outboard engines were required to be equipped with a full butterfly valve. The holes that exist below the area that must be covered by a Welch plug are low speed, idle fuel orifices. If the butterfly completely closes the carb rear throat, no air will flow, and no fuel will be drawn into the engine thru the idle ports. Just a thought. Try the butterfly from the other carb. Just a thought. R.T.