I have a converted homlite 30cc with electronic ignition on a Hanger 9 Taylorcraft, Wanted to know what prop I should be running.

I run a 18-8 Dyna Thrust on mine. Seems to do will. It sounds correct up in the air. Runs about 7500 with the magneto ignition.

I have another not on a plane but it will turn the same prop around 8200. It has C-H ignition.

This depends on how else the engine is modified.

The C-H ignition by itself will not change which prop to use.

Enjoy,

Jim