The reason your four-blade aluminum prop may have performed so well is that it's one of the newer Spitfire props.  They are an interesting combination of a "chop prop" style blade but on a four-blade build.  

 

I picked up two with different diameters/pitches as replacements for the standard three-blade aluminum prop that came on my 40HP four-cycle.  They offer both a couple of additional MPH and better hole-shot than the stock prop at a price that's considerably lower than a stainless steel prop.

The 4 blade props in my post are both Mercury Spitfire props. I’m new enough that I didn’t know they were anything innovative beyond the ad copy. 

Here you go.

Go run the 4 blade spitfire aluminum at max throttle and trim up as much as possible with out porpoising. 
Lets us know what the max rpms where.

 

If you run in current or wind test it in both directions and average the 2 readings.