Propeller for weed eater / string trimmer

I could use some help to finish this design. Please comment.
My weedeater jammed up at the end, so thought I could use the Motor and shaft to push a boat.
This prop started from the wonderful online here ( hope website never comes down )
https://www.wageningen-b-series-propeller.com/
I matched the size I wanted, horsepower and revs of weedeater, and then set up the blades to print in a strong orientation with minimal support in Fusion360.

I'd like some suggestions how to get the square drive from the weedeater to match up to my prop.
As stated above the bush bearing on my weedeater is seized so cant use that.
No idea if it will be strong enough to push a small boat.
Inspired by Thailand's long boats. Saw some vids on YT of other people's attempts but I think they always have the prop pitch too coarse.