The effects of various water quenching temperatures and duration time of aging on the precipitation hardened Al-7Si-0.65Mg cast alloy are investigated by differential scanning calorimetry, electrical conductivity, hardness and measurements of tensile properties. The results show a positive response to 95 degrees C water quench from solid solution treatment. The largest hardening rate can be obtained at 95 degrees C water-quenching and 60 min natural aging time. The tensile strength and hardness following a 95 degrees C quench are found to be superior to that of a 25 degrees C and 60 degrees C water quench for the shorter artificial aging time. High temperature water-quenching parameters available to high temperature (>180 degrees C) artificial aging with the shorter time are obtained.