If the Al was only corroding in areas that you can easily access, you could do the repair in those spots. But looking at your pictures, there's a siginifcant chance that there's more corrosion between the engine mounting bracket and pod. And, of course, the question is... how bad is it?
On a budget... lift the engine off, scrape and remove all flaking paint being VERY thorough, sand all scraped edges to ensure the paint is still adhered well and feather, sand the exposed Al to get rid of any embedded corrosion and clean. Then use a 2-part epoxy primer and then topcoat.
If you let it go... it will get worse - possibly to the point where you need to a buy a new one.
If you try to sell it with an obvious "patch" job, you'll likely have to drop your price enough to cover a new bracket... and in many buyer's eyes, a patch job = cutting corners and the buyer will wonder what other corners have been cut.
It's not that much work, really, to get it completely off if you want to go that route.
Just a heads up... the amount of "flaking" will easily be 3X the amount you think it is
