Wanting to paint an older boat that I picked up. The paint is old and chalky, some of it will come off on your clothes but its not peeling off anywhere. Should I sand down to bare metal or just scuff up the existing paint?

Take it all the way down. Pick a system and go with it. I like DuPont imron, it's the best and they're proud of it.

Imron is high as giraffe pussy, and way overkill IMO.

If its not flaking, u don't need to take it all the way down. Scuff it up real good with a red scotchbrite and paint.

Clean it first with a 50/50 mix of vinegar and water in a spray bottle. Spray it on and scrub with a scotchbrite pad. This will remove most of the dead paint. I've got a thread somewhere on painting an old boat. I'll go look for it.

http://www.tinboats.net/forum/viewtopic.php?t=12125 270Handiman's 1649 Custom Flat Project

Jump to post 16 for the cleaning part.

I'd think you should be able to get away with scuffing the paint with 120 grit them wipe it down with turpentine. Over and over until rag rag stays clean after wiping. I know that's what they recommend when you put gator glide on bottom so it should be plenty for new paint. Going down to bare metal should require primer before paint, scuffing existing paint would not because it is already primered.