[capnjim02]

the 31 you are looking at is actually a 30 that was modified to have a swim platform.
1980 and later models had cast iron keels or ballast if it was cb version. this was a cost factor. lead is more expensive than iron. however its also lighter in density. the 80 and later models wer 400 to 600# lighter in disp. but they had the same SA and the mast was moved forward to solve a weather helm problem on the earlier models. I think they are a lot of boat for the buck. well built but have a few places where they cut corners, I personally think that they did''nt cut as many as some of the other manuf. I love my 30 but then maybe I''m a little prejudiced. there is a web site for O''Day owners. www.odayowners.com
You can get a wealth of info on this site incl. all the specs.
good luck!