I switched to a 4 blade on my last two boats. Night and day difference once you get the right prop. Both on plane and in rough water.
What prop ,motor and wide open rpm you pulling now? I have a brand new merc spitfire that was a little ambitious for my 115merc on a 20 ft boat. i think it's a 17p and wouldn't turn enough wot rpm. I ended up with a 15. It may be a good fit. your welcome to try before ya buy.