Soz dolu reads "full of words" to me. This does not seem like natural Turkish wording. (I mean I cannot imagine one native speaker of Turkish saying this to another.) Is it idiomatic? If the boy is full of promise, he shows a lot of potential.

Retranslated. "full of promise" means umut verici, umut dolu.

To me, that means full of hope, which is inspiring or encouraging.

If I say my friend gives me hope, she is inspiring and encouraging. She is promising me that everything will be wonderful maybe.

If I tell a student that he is full of promise, he shows the potential to accomplish something wonderful.

I read promise as potential in this context.

What does soz dolu mean actually?

"Söz dolu" means "vaat dolu,gelecek vaadeden"http://www.wordreference.com/en...20of%20promise

I asked another Turkish speaker what soz dolu means, and he said nothing.
In this context, full of promise means the boy shows potential. I would not have thought umut verici or umut dolu could communicate this meaning.

I've participated your discussion with a new translation,
regards...

http://glosbe.com/tr/en/%C3%BCmit%20verici

Thank you all for the ideas. The dictionaries are of little help. Just because ten alternatives are listed does not mean ten are applicable to a given context. In the last, prornising is not a word.

Thanks:)