I run a pair of 18x26 cleaver 3 blade props on my 35' Cigarette w/ssm3's........don't see many that size around..are they not that common?....boat performs very well!

Back in the day we only had 3 blades. Then 4,5,6 and 7 blades.
Lower drive depths and deep V's liked the 3 blades for speed and carried the bow well. 4 blades brought better handling and fuel economy. Then the boat bottoms and designs caused the 5 blade props to shine.
I still don't have much affection for 6 and 7 blade props.
6 blades can band aid a issue or work well on a few set ups (racing cats and a few V's). 7 blades was the next step but don't have a place other than on a submarine. IMO

If you dial in 4 and 5 blades, you tend to get the best of all worlds.

Brett