Please prop help needed..
 

I have a Formula 312 Fastech w/ twin 454 mag MPI's I'm only running 67mph at 5150, hitting rev limt with 28p bravo-1.. 1.65 gears that puts me at about 20% slip... That sucks. Hydromotive wants me to use a 5 blade and go down to a 27p. But I have read some say their boat got loose on them.. Anyone have a good set up.. Do I just try 30p Bravo-1's or will I stillhave the same slppage..
I guess I need to have the ECM reprogramed too to et more out of her.