Propeller for weed eater / string trimmer

thingiverse

I'd love to lend a hand with finishing this design - can you share your thoughts? My weedeater jammed, so I thought I could repurpose the motor and shaft to propel a boat. This propeller started life at a fantastic online resource (fingers crossed their website remains up): wageningen-b-series-propeller.com. I matched the size, horsepower, and RPM of my weedeater, then designed the blades in Fusion360 to print with minimal support and maximum strength. Now I'm looking for suggestions on how to align the square drive from the weedeater with my propeller. Unfortunately, my bush bearing is seized, so that's not an option. I have no idea if this will be strong enough to push a small boat - I drew inspiration from Thailand's longboats after watching videos of others' attempts on YouTube. However, those videos often showed coarse pitch props.