make the brushes for the propeller and put an origin brush where you want the rotation point to be. Then select all of the brushes and origin brush and make them into a func_rotatable. Then just read the entity window stuff for info on how to change different paramaters of the entity.
Location: The United States of America... and damn proud of it!
I don't see how that would make any difference. The brush has no way of knowing where it is; you can start mapping at (0,0) or go elsewhere, with no effect on gameplay. Remember the level t3_hevil? With the cloaking device you had to disable? How do you think they made those rotating fans on the walls? It should work. What exactly did you do, step by step?