Narragansett Bay is a big place. My brother in law has an older GW 21 cc, so my feedback is based on his boat as a template. I think you're going to feel fine in the 180 on most days in the middle to northern parts of the bay, and Providence River on most days. I think the 180, like the 21, runs like a slightly bigger cc than it actually is. We're down in Newport full time.
However, like most other smaller open boats, in the middle and southern parts of the bay, you'll probably feel it when the SW kicks up against an ebb tide. And in a few spots, like the East Passage from Narragansett Bay to Mt Hope Bay, or coming in from Brenton Reef past the standing waves at Castle Hill, it could feel a bit dicey. I think if you're comfortable with a smaller boat in the chop that the bay can generate, and pick your day/conditions, you'll find that there's a ton of boats in that size range out on the bay.
180's a small boat, are you fishing with friends or out on the water alone or +1 all the time? I think it's too easy to buy too small for your anticipated "guest" list.