4 blade prop vs 5 blade

Godacious! · 12-19-2009, 06:19 PM

I am still playing with propellers on my 496HO/353. Some of my friends say stick with the Bravo 4 blades like the ones that came new on my boat. Other friends say go with the 5 blade. What are the advantages and disadvantages? Anyone have an opinion?

tcuda499 · 12-19-2009, 07:21 PM

I am in no way an expert in this field but I am learning so some one correct me if I'm wronge. A 5 blade will have less slip,better out of the hole but will also be harder on drives. Esp. on Bravo 1's. You will loose some rpm on top but your slip will be lower.I was looking into the same idea for mine but with a 38 and B1's much of OSO said to stay away from 5 blades. My X is also pretty low so I'm going with a spacer first. A 4 blade will slip more and your drives will thank you.

Barrydet · 12-23-2009, 12:23 PM

I have a 353/496HO combo also. The boat was delivered with Bravo 1 28's. With this set up, I would consistently turn 4700 WOT rpm's at 72mph. I typically travel with a full load of fuel (153gals). I am also very gentle while climbing onto plane.

Here is where the fun starts: I had a set of Maximus 15x30 from my previous formula 312. I did not want to them to go to waste. I consulted with Brett at BBlades. He performed some magic on the blades and trimmed off the diffuser rings. With this set up, I would consistently turn 4600rpm at 69mph. I noticed that the Maximus props pushed the boat out of the hole much "easier". I also noticed that my cruise speed at 3500rpm was 3mph higher. That fact equated to better MPG that I could see on my smartcraft display. I have been pleased with the performance of the Maximus props, but I have felt that I was at the bottom end of the WOT capabilitiy of the engines. I went looking for more...

This summer, I invested in the CMI Sportubes. Although the install process presented unforeseen challenges, Bob and Tanner from Full Throttle Marine, Spicewood, TX completed the project. I was seeking additional rpms at WOT. Here are the results: With the Sportubes installed the engines are now turning 4900rpm WOT at 74mph with the Maximus props. I am so pleased with this performance, that I have not used the Bravo 1's to get some comparitive numbers. I suspect that the Bravo 1's would provide some additional rpm's and mph. I plan to make the switch one day soon and try them out. I have also read that some folks are using Bravo 1 26's to get into the higher end of the WOT range. I hope to try that combination also just to see the results.

Hope this information is helpful, and by the way, all speeds were registered with a gps equipped speedometer.

4mulafastech · 12-23-2009, 01:14 PM

Quote:

Originally Posted by Barrydet

I have a 353/496HO combo also. The boat was delivered with Bravo 1 28's. With this set up, I would consistently turn 4700 WOT rpm's at 72mph. I typically travel with a full load of fuel (153gals). I am also very gentle while climbing onto plane.

Here is where the fun starts: I had a set of Maximus 15x30 from my previous formula 312. I did not want to them to go to waste. I consulted with Brett at BBlades. He performed some magic on the blades and trimmed off the diffuser rings. With this set up, I would consistently turn 4600rpm at 69mph. I noticed that the Maximus props pushed the boat out of the hole much "easier". I also noticed that my cruise speed at 3500rpm was 3mph higher. That fact equated to better MPG that I could see on my smartcraft display. I have been pleased with the performance of the Maximus props, but I have felt that I was at the bottom end of the WOT capabilitiy of the engines. I went looking for more...

This summer, I invested in the CMI Sportubes. Although the install process presented unforeseen challenges, Bob and Tanner from Full Throttle Marine, Spicewood, TX completed the project. I was seeking additional rpms at WOT. Here are the results: With the Sportubes installed the engines are now turning 4900rpm WOT at 74mph with the Maximus props. I am so pleased with this performance, that I have not used the Bravo 1's to get some comparitive numbers. I suspect that the Bravo 1's would provide some additional rpm's and mph. I plan to make the switch one day soon and try them out. I have also read that some folks are using Bravo 1 26's to get into the higher end of the WOT range. I hope to try that combination also just to see the results.

Hope this information is helpful, and by the way, all speeds were registered with a gps equipped speedometer.

Great info. Sounds like you are really getting her dialed in! Always good to have the engines able to run at their target rpm.

tcuda499 · 12-23-2009, 07:37 PM

are the Maximus 15x30 4 or 5 blade? nice call on the cmi's

Barrydet · 12-23-2009, 08:41 PM

Maximus is mercury's 5 blade propeller.

Audiofn · 12-23-2009, 10:17 PM

They are HELL on lower units!!!

James · 12-25-2009, 05:29 PM

How tough are 5 blades on a lower unit really,it is often a relationship of Hp, getting up on plane even if the props are 100 % hooked up you are only 3000 rpm or maybe 350 Hp, 4000 rpm 450 Hp, Bravos are rated @ 525hp. Yes they have less slip but you will turn a 4 blade XX time more to go the same distance. Anything over the rate Mercury Hp limit is when you start looking for trouble

Audiofn · 12-26-2009, 07:25 AM

The lack of slip is what kills the drive more often then not. That is why most recommend that you only run three blade props on TRS drive boats.

t500hps · 12-26-2009, 08:10 AM

4 blades will get more RPM than a 5 blade so you must drop pitch and/or diameter to match RPM's with the 5 blades (this is because of less slip). That slip does help save drives but provide less "bite" on the water. 5 blades typically loose a couple MPH top end, even if matching rpm with a smaller prop, but the 5 blade will have a much better hole shot and mid-rage cruise speed.