In short, I think the Carronades aren't OP.
Here is the long answer:
Many people say that the Carronades are OP, because they require generally a small amount of skills for a very successful strategy. But that is simply wrong in terms of game design, here is why:
http://www.youtube.com/watch?v=EitZRLt2G3w.
We need strong carronades, I consider them pretty much to be a hard counter to Junker and Galleons. If we weaken them, we make those ships indirectly even more useful. Most of us will agree that those ships of all don't need a boost.
When you carefully read the comments you should notice that the disagreement is not in how powerful the carronades are, but how accessible, how easy counter strategies are. How much skill/knowledge you have to gain in order to counter the carronades.
The other point is, after the latest patch we gained a lot of different options for medium/long range, which was earlier just mercury and gat/mortar/flak combo. But for short range, the Carronades are pretty much the best choice there is. There is no OBVIOUS short range combo that can be used against the carronade.
On longer range though, we do have effective choices, but adapting to a long range strategy might be a bigger learning curve for newer players.
So maybe what we really need is a good, easier to find short range counter to the carronade. It should be harder to execute, that is fine. But it should be a very obvious counter, so that players can say: "I may not be able to right now, but I know how I can put an end to those pesky Blenderfishes!"
To summarize: in this thread, we already hit some solutions. But they are all worthless as long as we haven't nailed down the problem we are trying to solve. Some people are pissed off at the carronade and bring forward solution to a problem we haven't yet nailed, bad solutions in short. That doesn't mean their reasons to hate the carronade are wrong too.
To summarize the summary: Go flamewar lulz