EVINRUDE dealer from Chania (Greece, Krete Island) has advised me to try EVIN REBEL 19".
I have good experience with 4 blades also. My spare is Korean ALU 4 blade:
The same top speed than VIPER, not so perfect acceleration and go to plane like VIPER but better fuel consumption on 3800 - 4200 RPM. Everything with Family on board (5 persons).
Full load (9 persons) - VIPER does better (speed and fuel economy)
I think that I have maximum possible engine for this boat. 115 HO is downgrade 135 if I remember. So my set accept even so big props without any problem.
Now I have problem - which one test next ? Merc Rev4 or REBEL 15 1/4 x 19"
Some dealer told me that REBEL is for V6 only but the same has been mentioned about VIPER 14 3/4 x 19.
115 HO has bigger gear-case than normal 115 I think.