I had a similar problem with mine. The last answer is an "elegant" solution, but mine is a little more agricultural
I bought a brass female to male adaptor of the correct size (I think it's 3/4"). I drilled three small holes at 120deg through the female end and tapped them to take a screw. Using a drill, I made 3 "dimples" in the aluminium outlet of the washer that lined up with the 3 holes I drilled in the coupling. Used Araldite (or similar) in the female end of the coupling and screwed it onto the pressure washer and then tightened the tree screws to locked it into place. Did this over a year ago and it's been ok since
Brian
April 2009