All that is stamped on the prop is "8.5". No other markings. I know it is a 8.5" diameter, but I assume the stamp is for the pitch? I want to drop about 1" in pitch and I think Tohatsu makes 6.5, 7.5, and 8.5 pitch sizes, while Solas has all pitches at 7, 8, or 9. I just want to know if I should...