My father used to use those kits checking for cracks in the propellers of unlimited hydroplanes way back in the 50's when he was crew chief of several wining boats. Saw the kit being used a few times.
Losing a blade of one of those propellers used to do great damage to the shaft and bottom of the boat. Interestingly enough, those propellers, usually two bladed, at that time were made by an outfit in Italy who had never seen an unlimited hydroplane. Tended to throw a blade now and then because the material was not all that good. Now, they are better but still can throw a blade.
