Don't play around with the voltages. If they are meant to work at 1.65 they can work at 1.65volts.
You can use 1.65 on that motherboard if it is not set to that value by default just change it manually.
You can make the ram to work at 1.5 volts but why do you wanna do that?
Increase the timings, decrease the frequency and decrease the voltage.