I'd categorize both of those as sailboats. Yachts are something else altogether. Then again, I live so close to them that I see the really big ones often. Just because it's too big for a crick in Colorado doesn't make it a yacht!
Starting in Louisiana, I'd go to Fort Jackson and Fort Pike.
Heading into Florida waters, Fort Pickens would be nice from a boat, I think, though I haven't made my way there. You could visit Fort Barrancas while you're there, since they're right next to each other.
I'm about 30 min from Ft. De Soto, so of course it was the first one to come to mind, but I don't think viewing it from the sea (more appropriately the Gulf) would be terribly spectacular, though it is a nice fort and park. We could meet up for a barbeque and have a Morko reunion if you sailed up sometime!
I've wanted to visit Fort Jefferson at the Dry Tortugas National Park, but never made it there. I think it would be a very nice one to see by boat (you have to get there by boat anyway). May as well stop by Fort Zachary Taylor while you're sailing by Key West.
Of course, Fort Matanzas and the Catillo de San Marcos would be cool by sea as well.
Moving up the coast, I'd definitely swing by Fort Clinch on my way to Georgia.
In Georgia, I'd want to go to Fort King George, Fort Pulaski and Fort James Jackson. Fort McAllister would be fun to explore if not so interesting to view from the water.
I don't know how much further you'd be going, but I'm sure there would be some nice places to visit all the way up the coast.