Ahoy, there lads 'n' lasses! I've found several photos of ships being filmed for Pirates of the Caribbean 2 & 3. There's even video at the bottom of the page which shows the Black Pearl firing cannons! You can see the cannons being pushed out, then test-firing all on the starboard side. Enjoy, folks!
Oh, you probably want the link, too!
Edited: Sorry Mad Matt, but Disney legal is hunting for those who post the pics. To keep the pub from coming under scrutiny, we cannot post pics or links to it here. But if your so inclined, you can respond to those who pm you privately.