I would start off by dropping the Multiplier to say 10 and then upping the FSB till I found the limit of your mobo and memory, when you have some idea of where the limit is then start to play with the chip itself and go for the highest FSB and multiply combination you can achieve.

You should be pretty safe to bump up the voltage to the chip, memory and chipset up a few notches.

Seeing your water cooling lack off cooling from the CPU cooler to mobo compoints around that area can sometimes be a issue, a 120mm fan blowing at low speed at the area where the Cooler would have been quite often sorts that out (I used to test with a desk fan blowing into the case and if I had any issues when I turned it off, I would then add the fan inside the case)