need help
 

my 98 25 thunder w/ 500 hp 12" ext box runs as follows

26 4 blade predator prop labed it runs. at 3500 rpm 38 mph
at 4000 46 mph wot 72 mph.

i bought a new out of the box 26 4 blade bravo 1 with the plastic insert you put in. at 3500 47 mph at 4000 54 mph wot 68 mph
at 4700 rpm. i cant figure this out the bravo is appx 9 mph faster
up to 4000 but at wot its slower and only spinning 4700 rpm.

these speeds are on a hand held gps w/ trim and tabs in same
position.