Two non-centrosymmetric superconductors Mg9.3Ir19B16.7 and Mg11Ir19B15 are synthesized. The normal state electronic coefficient of specific heat γn, the Debye temperature ΘD and the superconducting upper critical field Hc2 are found to be sample-dependent, while the electron-phonon interaction constant λ=0.58 and the normalized specific heat jump ΔC/γnTC=1.66 are sample-independent. The higher superconducting transition temperature (TC=5.7K) in Mg9.3Ir19B16.7 is found to be due to the higher density of states and higher Debye temperature ΘD compared with that of Mg11Ir19B15. We also obtained other characteristic parameters of both superconductors, including the Ginzburg-London coherence ξGL, penetration λGL, lower critical field HC1 and thermodynamic critical field HC.