Remix of this water jet drive
and nozzle attachment.
This was scaled and tweaked to utilize standard 3mm shaft, and M3 screws, while being driven by a 540 RC motor. As originally designed, I believe it was designed for a 400 series brushless, but I didn't have any of those. However, I did have a large collection of 540 size brushless from my days of running RC trucks.
I also modified the bearing carriers to accept MR93ZZ bearings. If you have any other bearings you would prefer to run, let me know and I can easily modify the stl to accept other bearings / shaft sizes.
Note that I haven't actually printed and assembled this yet, so do so at your own risk of wasting time and filament. I will update when I assemble it as to any tweaks I had to do.
Edit: 2019-03-19: Added a 3 and 4mm shaft option for the prop and jet housing. Updated clearances for M3 hardware.