ORIGINAL: jedijody
I wouldn't rule out a mismarked prop, borrow a prop and retest. If it is doing 8300 then it's a new record, enjoy it while it lasts but I'd wear a helmet and flack jacket anywhere near it. It's a well known fact that an engine will run the best and most powerful right before it grenades.
Jody, I'm sure this engine will turn those RPM, with little load (pitch) on the prop. But that's just beating the air 1K past the sweet spot on the DL. With a 22-8, mine turns in the 71-7200 range, and pulls like a Mule in a bog hole..