I just used Klean Strip Stripper from walmart. I've got all the paint off of the boat except on the bottom.
Some things I've learned:
The warmer the better. This is the most important thing. The stuff just doesn't work nearly as well when cold.
Be liberal when you brush it on. I had to be careful to not slop it everywhere when brushing it on.
Let it sit for plenty of time. I found it's better to work on a couple different things at once, and just let the stripper sit on for awhile. 1/2 at least.
Sometimes you will get better results when adding a second slathering before taking off the paint.
Finally, tied for the most important thing is to forget the scraper and get a stiff stainless wire brush. I tried using one in a drill, and to be honest I think the hand brush works better, and is less messy.
I never could get all the way to aluminum everywhere with one coat. The factory zinc coating was particularly tough.