I ran this engine (w C-H ignition) two seasons ago on an 80" w/s ISC clipped wing Cub. The previous post is correct in that an 18 x 8 is the better prop for this engine. The engine was a good combo w/ the Cub and an overall good performer. However, I did think that comparatively it was a little heavy -- you've got to match the engine to your application. Best of luck!