Since the Radeon 7200 runs at a core and memory clock of 166MHz (I can't believe I know that...) than you probably could get it stable around 183MHz, but you may be able to pump it above that. Overclockability varies from card to card, especially ones with good cooling. I assume you have the stock cooler. In that case, if you don't have a heatsink over your memory, I wouldn't try to raise the memory clock above 180-183MHz.