Quite sorry for my rather incomplete post earlier.

Skeeter, a lot of people will suggest a lot of things (that includes me). For a sports trainer (as I think you have), you should either put 11x6 or 12x6 if the model has the ground clearence. 4 and 5 pitch props are also good but use them as a last resort if you are most uncomfortable with the above.

By any chance, did you adjust your throttle pushrod linkage about the same time you lost the prop? Or you may have lost the throttle alignment. Meaning, what you think is 50% throttle on the stick may not be 50% on the carb. Just check by observing your carb while operating throttle on your TX. It the alignment is lost, readjust. You will find a lot of info on other threads on how to do this.

Normally for your app, 11x6 should be quite good

Ameya