My 1 HP pump runs well if the pressure switch is set at 30/50, but if I crank cutoff up to 60 it will continue to run, with the needle hovering below 60. If I set it to 58, it will cut off, but not as quickly as if I set it at a lower pressure. Is something wrong? Or is 58 psi about all I can expect from a pump of this size?

(Further Info: Myers model # unknown, impeller and seals replaced recently, A.O. Smith 1.5 hp 3450 rpm motor (ST1102). Well depth, unknown, water table under 6' (Florida coastal). Pump sits right over the wellpipe with a brass check valve in between. Pump puts out at least 15 gpm through a nearby hose bib. Gauge on pump has been replaced to verify accuracy) 45 gal galvanized tank.