What coud cause a hoarse voice but no pain in the throat?

Several: Laryngitis (inflammation of the vocal cords) from a cough or vocal "overuse", acid reflux to the voice box, vocal cord nodules or polyps are common causes. If voice rest does not help this within a week or so, or if you are a smoker, you should get this checked to make sure it is nothing more serious. Sometimes voice box cancers can cause hoarseness without associated pain.