I purchased one of those from Lowe's and installed it in my 16' Scamp
but was not happy with it. I don't know if I got a bad one but I returned it and bought a 6,000 BTU from Home Depot that I am much happier with. In the stock location I would not have been able to remove and clean the filter on the 5,000 unit but the filter on the 6,000 removes from the front.
It is great the way the 5,000 fits in the window and certainly should cool a 13'. It is certainly more efficient a location shooting the air straight out instead of having to turn 90 degrees from the stock location. We spent a week at the beach a couple of weeks ago (end of May) and our new 6,000 ran 24/7 and did a good job cooling our 16' but certainly was not too much unit. It was about maxed out physical size wise in the stock location and I am glad I took the trouble to cram it in there. I saw a 8,000 BTU unit at WalMart the other day, think it was a Hier, that did not appear to be much bigger physically than my 6,000.