As a rule The 3 blades ran good on the twin engine ZX boats out of the box. Not to say though that a 4 might not get you a little more, however they usually ran those on the single engine zx hulls. The drives are done for speed As sideways mentioned. Spinning them the other way will probably slow you down. The 28 Scorpion was more of a limited edition 28 due to the 377's in them and thus the Scorpion graphics on the deck (most models).. You should be grabbing high 70's to very low 80's on that hull if set up right depending on where you boat..
Jamie / Lakeside Restorations