First-and second-order polarization propagator calculations of magnetizability, rotational g-factor, spin-rotation constant, and hydrogen and oxygen shielding propterty surfaces are reported for the gas phase oxomium ion. Using these surfaces and the nonrigid inverter ro-vibrational eigenfunctions, effective magnetic molecular constants are obtained for the lowest ro-inversional states of H 3 17O + and D 3 17O +. The predicted constants exhibit sizable and non-monotonic dependence on the vibrational and rotational quantum numbers. We find nearly temperature independence of both the 1H and 17O shieldings, mainly due to cancellation effects between contributions from the inversional and the symmetric stretching modes. We compute a downfield shift in 1H as well as 17O shieldings of H 3O + relative to pure water in agreement with earlier observations. The influence of hydrogen bonding on these shifts, as well as on the deuterium-induced isotope shifts on the 17O shielding, is discussed.