Reporting back on the Merc Spitfire prop. I went from a 3 blade Black max 21P to a 4 blade Spitfire 21P (Merc recommends staying with the same pitch for this prop.) Running a 5.0 Mercrusier Alpha 1. With 3 blade, Me, wife two kids and cooler, full fuel I was at 4900 RPM's at WOT 50 mph. This...