Hmmmm mismatch B3 props. [Archive] - MidwestBoatParty.com

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DaleM

11-26-2008, 01:04 AM

Driving along the other day I started thinking about prop performance on my Rinker 270. I realize it is not a "performance" boat however I do notice different levels of performance when I run either the 24" prop set or the 22" prop set. Obviously I get out of the hole much quicker with the 22's and my top end is better with the 24's. What would happen if I ran a 22 with a 24. Say I was looking for a little better top end with out giving up the hole shot. Could a guy run the larger diameter prop with less pitch in front of the smaller prop with more pitch to accomplish this? Or vice versa for that matter? Has it ever been done and short of wrecking the drive what is the down side?

LA69MM

11-26-2008, 09:33 AM

I have heard of people playing with this. Give it a try. Let us know!

fohbuddha

11-26-2008, 03:01 PM

Have you tried talking to Brett at BBlades? maybe he could shed some insight. The worst that could happen is you will loose performance by trying it. Just put them back the way they were. Let us know what you do.

Buddha

BrettM

11-26-2008, 03:40 PM

Never heard of doing this. I would be concerned about spreading the load equally along the prop shaft. Maybe it can be done, Brett from Blades might know the real answer. I know on some triple engine stuff the middle prop might be a different pitch, not sure on a single Bravo 3.

fohbuddha

11-26-2008, 03:52 PM

That is a good point, but would the pitch really be a factor on the pressure that is put on the shaft? Is the diameter more of a factor? I would email Brett at BBlades.

Buddha

Never heard of doing this. I would be concerned about spreading the load equally along the prop shaft. Maybe it can be done, Brett from Blades might know the real answer. I know on some triple engine stuff the middle prop might be a different pitch, not sure on a single Bravo 3.

BrettM

11-26-2008, 04:01 PM

Both would come in to play. Your on the right track, call Bblades!

BDM

11-26-2008, 04:03 PM

I'm not an expert at props, that's for sure... but it would seem to me that if the pitch is higher on one side than the other, it would cause steering problems, aka one side pushing harder than the other would require some oversteering to that side to compensate for the extra "bite" of a higher pitch prop.....

BrettM

11-26-2008, 05:42 PM

BDM

11-26-2008, 05:51 PM

Hmm.. so it's a dual prop... duh, should have got that from the B3 thing if I had actually paid attention while I was reading...

In that case, if you put the 22 in front of the 24, I would think it would work...

If you did it the other way, I would think it would cause the 22 on the back to cavitate some? Just a guess... hell, could be better the other way.... you need someone that's very experienced in fluid dynamics, and I haven't taken that course yet... :oops:

DaleM

11-26-2008, 07:00 PM

I've seen in some instances where they are running a 4 blade in front of a 3 blade on the B3 drives. If anything would be goofed up I think a combination like that would surely do it. I will mess with it next summer.

bbladesprops

01-03-2009, 09:00 PM

I just wrote a LONG disertation on the history of the B3 set up. It got deleted due to ispell stuff. I can't, I mean wont re type it. However.........

The 4 front 3 rear was a accident due to trying to prevent cavitation burn on the 3/3 set up in 2000 while I was working at Mercury Racing. Big HP was burning the blades at Formula when they mated the 500 EFI's to the B3's.

We played with higher rear pitch over front pitch for a couple years on the old Blackhawk drive a number of years ago. There are tricks to these things. Loads are harder with higher pitch but it is translated to the gears not the shafts.

We due many custom tweaks to dual prop set ups at BBLADES. I like the 3/3 sets better than the 4/3 for customizing. The 4/3 only offers low end and in some cases cruise benefits.

B