This is a derivative of Skimbal's CD-Rom motor pump, thingiverse.com/thing:4881, but with screw mounting and a 6mm circular outlet. Youtube video of it here: http://youtu.be/us2KlyBPEaU
I may design a V2 sometime, possibly without screws and without need for any support material.
1) Print out parts. I paused the print of the housing partway through to brush some oil on the support material around the shaft. That in theory makes it easier to remove later.
2) Remove support material from the pump housing where the shaft will go. This allows the motor to rest flat against the plastic.
3) Screw on the motor using two small screws. If the motor shaft does not spin freely then you may have to drill it out a little.
4)Press the impeller as far as possible onto the motor shaft without it rubbing.
5) Spin up the motor and sand down the impeller blades until they are just below the top of the pump housing.
6) Using a hot glue gun, glue on the lid and make sure it is completely sealed around the edges. I had to raise the lid up slightly since I was lazy sanding down the impeller.
7) Power it up and submerge in water. On my version a little bit of water did start seeping out the motor itself.
You can also use the pump as a generator using either an air compressor or vacuum cleaner. don't run it for too long otherwise you will wear out the motor bearings or brushes.