Translation:The boy eats, but he still feels hungry.
I am going to argue that "but yet" is borderline grammatically incorrect. The primary use of the word in Modern English is as a coordinating conjunction (a conjunction that couples opposing ideas). This is also the primary function of but. Using them both together is redundant. However, in older modes of speech you could find "but yet" used so I cannot really say it's ungrammatical. "And yet" seems more natural too me as "and" is only a simple conjunction and is not used only to couple opposing ideas. http://grammar.ccc.commnet.edu/grammar/conjunctions.htm#yet