I removed many many years of bottom paint from my AS. I tried the chemical stripper. Peel Away and another brand made for marine use. I have heard of people having good results, I didn't. Chemical won't remove multiple layers. Multiple apllications are neccessary. Leaves blotches of thicker paint (looks like measles) that then have to be removed. Softens gelcoat (even though it says "won't attack gelcoat") Will scrape away thin layers of gelcoat when removing paint.
The method that worked best for me was to use a 3" wallpaper razor scraper. I was able to knock off a lot of loose material and scrape it clean in some spots. Some nicking of the gelcoat occured but nothing serious. Takes a little getting use to . I did slice into a former repair, then had to grind out the repair only to find it was done properly( except for the slight bulge it left). After no more material could be scraped I used a 5" random orbital sander to grind away the rest of the paint. An orbital can be held flat against the surface. Circular sanders,polishers,drills will leave swirl marks. An 8" orbital will work quicker.
Bottom was in pretty good shape for a "71. Some small chips and a lot of small crazing (S cracks) in the gelcoat. I filled some of the chips with Interlux Watertite compound. Not really neccessary. I did a finish sand with an old 1/2 sheet sander with 80 grit. Wiped entire hull down with acetone. Some small areas of gelcoat were ground through to fiberglass. I used Interlux 2000E epoxy barrier coat so I did nothing to the bare fiberglass areas before application. Two gallons got me exactly 4 coats on my 222. Very sticky stuff, think about thinning the first coat or two. They give you a pretty good window between coats. The first coat of bottom paint is the most crucial, only took about 1,1/2 hours after last coat of epoxy before I applied bottom paint. Use the REDTREE Marine Rollers ONLY! And to reduce fibers in the paint even more, wash the brand new rollers with fresh water and let dry completely. I finished with three coats of Micron Extra. It's a dirty, nasty job. Don't scimp on price or materials. The bottom of my 22-2 is beautiful.
