Apapa,

If we chose to believe the Rossi claim, of 1.9 HP @ 17,000 RPM and it would do it spinning an APC 10x6. Well, turning the same prop at 25,500 RPM will require over 6.4 HP, IF we don't talk about compressibility...
Your blade tips are doing 339 m/s; almost Mach 1. Some places on your prop blade profile are going supersonic. That will require even more HP.

Sell them on Ebay... But tach them again with another, different tachometer.

Sincerely