I am looking for a DVD sterio for the bost but the installation is a
challenge. I need a head unit and a remote dvd unit. The head unit
cannot be deeper than 4". Can anyone help with a suggestion?

Where are you planning on putting this head unit? There aren't going to be
many radios that are only 4" deep. Get a normal radio and use wired
remotes; sony, clarion, jvc and others make several suitable for marine use.

And for pity's sake, get a spell checker.