Mitch,
I sailed my O'Day 222 out to Block from Newport RI back in the mid 1990s and it was a horrible trip. I didn't enjoy it. I sailed into New Harbor and went ashore. Shortly after that, my wife and I took a ferry boat over to Old Harbor in Block and I wasn't very impressed with that island. I'm sorry if I have offended anyone with my assessment of Block Island, but I'll never go again. With that said, these boats can take more punishment than we can. I'm just not too fond of swells and tidal rips. I've made the trip to Martha's Vineyard and Cuttyhunk Island for many years and I prefer these Islands to Block, but this has nothing to do with your question.
I think that the O'Day 240 is a capable cruiser for these waters but I think that you need to get used to her and find out for yourself exactly what she is capable of doing in your area waters under different weather conditions. Learn to put a reef in the main when the winds start to kick up, and shake it out when the wind dies down. In other words, get out in your boat and get familiar with it first in your sailing area before you take any long trips. These waters can be brutal. I guess that's why I prefer to sail the river and the bays in my area. They can even kick up at times.