Schwalbe UK's website lists the 1.5" Marathons with a range of 45-100 psi.
http://www.schwalbe.co.uk/c2-1073-sc...-marathon.html I've been running mine at 85 or thereabouts with no problem, though I haven't checked the pressure in a while (and I might run the front a bit lower, no suspension on there so a little rough on some surfaces). You should be fine on those.