How would a evinrude 25 hp 2 stroke do on a ALUMACRAFT 14-FT. FLAT-BOTTOM BOAT?

Depends on the boat manufactures recomendations. 15 feet would be better. I think 20 hp is max for a fourteen foot boat but i guess 25 wouldnt hurt. if the 25 hp is running good you should push the fourteen footer pretty fast. just be careful.