Thoughts on Carver C40 for Coastal Cruising & Loop

Quality on Carvers is just ok. Not good or great. I ran a new 52' flybridge and a coupe a few years back, ride was not great to say the least. For the loop you should be ok, if you really pick your days on the lake crossings and stuff, most of the loop you can do on inland waters. In that size there will be a bit of compromise when it comes to doing the loop. Easily do-able, you just can't be on a tight schedule when you do it.

Nice things about Carvers is that they're roomy, and that's important if you're going to spend long periods aboard (such as when doing the Great Loop). Sure you'll pick your days but you do that with any boat, and cruises like the Great Loop are meant to be fun. Getting pounded and wondering if you'll get to live aren't fun. That said I've run a 44 from L.I. to Nantucket in the middle of a major Nor'easter with gale force winds, and a 37 from NY to Miami including 8' following seas from Beaufort to Georgetown. The C 40 would be fine for that kind of cruising the OP mentioned. Comfortable, shallow draft, decent handling and economical both buying and running. Two things to check though: DK if what you're looking for is gas or diesel but you want diesel. The gassers don't have the range you'll need. Also if what you're looking at has a radar arch or hardtop it'll probably need to be dropped at places on the Loop.
As for how they handle Florida conditions though, not great. Florida boats get a lot of abuse from the heat, sun and warm salty water. It's fine to go there, but if you're looking to buy I'd concentrate my efforts up north. I think there's more Carvers up north anyway

I believe he’s talking about buying a new boat

No he said "late model". That's not new. 1st sentence.

Yes Carver has vastly improved since the models from say the 1980's both in fit and finish and in hull design. It's a mid-value boat, neither the best nor the worst, but quite respectable and with good manufacturer's support. She'll handle the Florida weather as well as any, but when buying I'd look for one up north that hasn't been subjected to the conditions there for extended periods. I'd give that advice to the buyer of any boat. Florida weather is hard on boats.
3 years old is a good time to buy IMHO. Old enough to have the new boat bugs worked out but young enough not to have experienced much abuse and neglect.

Agree w/ NYCap's 2 posts; as far as hardtop/arch issue, all you'll need is less than 19' for the loop [Burlington Northern bridge just south of Chicago] which shouldn't be a problem.