I have a new alu propeller SOLAS AMIT 3x7 1/4, pitch 6, on the left on picture.
I need advice, not sure it will work with my set up : 12S,
Could work if you have a gear?
My first prop was : Solas 0001-073-06P Low Horsepower Plastic Boat Propeller.
It’s a different model, but same diameter and pitch so it should work.
I used it direct drive on 80100 80kv with 12s and worked fine.
however,the prop highlighted here: 80100 direct cooling - #286 by Mat - Builds - FOIL.zone worked much better! 
yes, using a 5:1 gear