3 vs 4 blade

The less blades you have on a prop, the more efficient it is. It's much a matter of HP and diameter. The key limitation is prop diameter and how much power you can transfer per blade. The more blades, the more power you can transfer, but also the more drag you encounter which wastes power. A longer blade also has more leverage and less slippage transferring a greater percentage of power per blade. Smaller diameter more bladed props spool up to speed quicker and will get you on the step faster, but won't be as efficient once you're there.

Call Frank and Jimmy's prop shop in Ft Lauderdale and talk to them to get you set up with the best prop for your application.

I have a 1982 42' Post. My Capital gears had to be replaced. I went with Twin Disc MG5085SC gears but the ratio was 1:1.42 vs 1:1.54 for the Capitals.

At first I could only get one gear, so I put it in on the port side. The props originally were 3 bladed Columbias 26 x 28. I put a new 26 x 27 on the Twin Disc side. The result was bad noise and vibration. I thought it was the install but nobody could find anything wrong.

It was a big decision to put the second Twin Disc in because I thought I might be throwing good money after bad. In the end, I put it in along with a set of 24 x 27 4 blade custom wheels that were actually cheaper than off-the-shelf Columbias.

The boat is now smoother than it was originally and speed is what it was before I changed gears. It actual seems a little faster at cruise.

Since I changed the gear and the wheels at the same time, I'm not sure exactly what made the improvement. My theory is that the 3 bladed prop didn't have enough blade area to carry the load at the higher shaft speed.

Engines: 6V92 J&T 530 HP
2300: 29.7 knots
1900: 23 - 24 knots

Kapoc,

One thing for sure, you will notice a tremendous difference in the "bite" of those four blade props at low maneuvering speeds

Kapoc

I'm no help on cost estimate, but do suggest you stay with nibral for durablity.

I would suggest calling Ralph at Digital Prop Shop at Herrington Harbor North Marina, 389 Deale Road, Tracys Landing, MD 20779. Office phone is 800-804-7757, cell is 410-867-8878.

He got me some kind of custom props from Asia. I don't remember the name, but he'll know. They were cheaper than Michigans and the blades looked very sophisticated.

He recommended 26 x 28, but because I was a little overwheeled before, I went with 26 x 27 which are near perfect. This is with 1.42 ratios on a 42 with 530 HP 6V92s. The numbers on a 46 with 6-71s would probably be a lot different.

Disclaimer: I make no money from this. I hope it helps.