Switching to 4 blade on 25 hp

[1973Chieftain]

I recently bought a new boat, a 1748 welded aluminum modified V duck boat, dry weight of 550 lbs. I put my '85 Johnson 25 hp on it, currently has a general purpose aluminum 3 blade 10x13 prop. My normal load is 600 lbs of people and gear. It currently tops out at 25 mph, sorry I dont have an RPM gauge on it which I know makes this more difficult. I am looking for more low end power for easier maneuvering in the fall while hunting which is why I'm thinking of a 4 blade aluminum. The current one is dinged up so I'm looking for a replacement. Normally you go down an inch in pitch when switching to a 4 blade I believe- with this style and weight of a boat, would that general rule hold true or should I be looking at some other pitch? Thanks!

 

[Sea Rider]

You should be looking to install an induction tach firstly prior going blindly ordering a new 4 blade prop. Test current prop no matter if dinged on a wot spin on flat calm water cond to check max achieved wot rpm as usually loaded. Ideal is propping an OB to run middle to max wot rpm range factory stated.

Happy Boating