Using 80 lb. bags of "type N" mortar for Ledgerwood stonework, which will be applied to a vertical wall of concrete, what should the consistency be? How much water is too much?

You might find an answer to your question (and any others that you might have) at this web site:

Masonry Magazine: Mixing Mortar (http://www.masonrymagazine.com/9-02/mixing.html)

Have fun!!