Pressure depends on the rating of the tire. Maxxus makes a 10 ply that runs at 80PSI. Regardless, the max pressure rating(cold) is on the sidewall. Run them at that and remember that ST tires are only rated for 65 MPH.
2015 Seaark 1872 MV CC Etec-90
Helix 12 CHIRP SI, HB 1199, MinnKota Riptide ST80/i-pilot Link, Bob's Hydraulic
Bitter Gun Owner