I have a 31 foot Scarab II with new power coming in 4 weeks. Twin 565's 675 HP each TRS Drives 5500 Redline.

Should I go 4 blade or 5 blade? Pitch? Speed?

Any help is greatly appreciated.

I would start with 30 Pitch 4 blades,,,and go from there .
Its hard to tell,,,32 maybe even 34 ,,i also recoment to use Bravo 1 props , not Hydro's,,the will snap blades with heavy V's !!

Had a 30 Scarab with twin 468's 650hp each. Ran 82 with 3 blade Mirage props 27P I would agree with Daredevil and start with the 30's or even a 28P 4 blade. My 2c's.