It turned out that it don't runs straight ahead if driving this boat with an impeller. It runs more like a drunken sailor ;-)
Therefore I designed a kataraman that has much more directional stability.
This time I got something bigger for testing - a bath tub ;-)
I used the same drive again that Oliver designed for his impeller-truck :-) http://www.youtube.com/watch?v=h_ZOYQsWkps
There are two different parts. One (Micro USB Plug hole) has an open hole to fasten with a 2 mm screw.
You can also use two of the parts with closed holes and glue them together.