Many alum boats...
I have had several aluminum boats out here on the Chesapeake Bay, not quite as salty as the Gulf, but salt is salt. Here is what I do:
1) First part of year I clean it up good. Then apply some WD-40 to screws, seams, and other such parts. If I find any screws or such that are rusting/corroding, I pull them out (assuming you can)...and replace them with new marine grade stainless. Mind you, I have only had to replace things about 5 times over 25 years...cost me about $30.
2) There are lots of choices for plates...just find ones that work for your boat. These should be replaced at least every 2 years, or every year...depending on deterioration
3) After EVERY outing, wash down EVERYTHING with fresh water.
4) After you wash it with fresh water, give another quick bath with something like "Salt Away"...just attached the connector to the hose and spray away. You can just leave it on the boat. Remember, plain water will NOT take out all the salt, it can create bonds with the metal...using something like Salt Away will take away those last bits of salt...also great to use when flushing the motor (and it is environmentally safe to boot).
5) At the end of the season, do #1 again.
Thats' it...once you get a rhythm down, you are talking about a whopping 10 minutes for wash down, and maybe 1 hour prep-time at the first/last part of the year. 25+ years from now it will still be working/looking fine...hell, I still have a 1950's 7.5hp Evinrude I put on my sons first boat (the one I mentioned above)...damn thing probably weighs as much as he does!