Re: Air Cooled Outboard Overheating

[frankr]

No, that diaphragm is not what I meant. Some have a 1/4" diameter X 1/2" long (usually orange) fuel pump bladder inserted into the carb’s mounting flange. A pulse hole in the gasket aligns with the bladder.

The one you replaced acts like a float. As fuel is pulled from the chamber above it, the diaphragm moves upward, which opens the inlet needle & seat, allowing fuel to flow into the chamber. As the chamber fills, the diaphragm moves downward, closing the inlet needle & seat. Process constantly repeats. The chamber above the diaphragm must be air tight so a suction can develop to pull the diaphragm up as gas is consumed.