370, 3350-3400 rpm wot, yanmar, right where it should be, 22x20 prop..5 blade does it lessen prop noise , increase ,decrease rpm, advantages, disadvantages. everything is fine with 4 blade, but a little noisy on hull ?
Flowers Boat Works 46 hull #1, Flowers Boat Works 36 hull #1, Wayne Beal 28 Hull #1, Repco 30 1968,
Normally you would go with a 5 blade to increase surface area where diameter is a problem. Generally they are super smooth but do not necessarily increase or decrease performance over a 4 blade. If diameter is what is causing your problem you could run a smaller 5 blade and that might solve the noise issue by giving you more tip clearance. Cup could also help by holding water on the blade but not without changing pitch or diameter. Most folks including myself that have changed over to the Michigan DQX 4 blade propellers have been very happy with how smooth and quiet they are on the DE hulls.
I'll second the DQX.It also turns a little harder than a regular 4 blade.It did away with 90 % of my prop noise.I tried a 5 blade and I didn't care for it.The thing reminded me of a three blade,kind of like having a baseball card in your spokes.