Brett-
I just completed some back to back tests Bravo 1 vs Hydromotive QIV. The Bravo is a factory labbed 25 pitch from Mercury Racing and the results were almost identical to the Hydro. The hydro slightly beat it in speed at every RPM range. What is odd is after 4000 rpms both props began to increase in slip. The boat is a Formula 292 SR-1 and the water was glass smooth tonight, could this be the issue? I'm using 24 as the pitch in the calculator as I know the pitch on a Bravo is about 1 off.....

Here are the numbers.
Bravo 1
RPM/MPH/Slip
2500/29/23%
3000/36/21%
3500/44/17%
4000/54/11%
4500/60/12%
5200/66/16%

Thanks for any input on this.....

endeavour32,

Hello. I did reply on the other thread that was going.
You would actually want to use 25 as the pitch in your calculations since the casting used is probably a 26 (831914). Pitch reading it will on our MRI machine will get you in the high 24's. The cup heights will put you in the low 25's and your version will be very close to 25. So, your slip is higher than you think. This is why I stated the Bravo 1 prop comparison to the Hydromotive is skewed. The hydro is 1/2" in diameter larger with taller cups so it will be better in the mid range.
You are stating here that numbers are very close between the two. What are the Hydro numbers?

Sometimes I'm hesitant to give away too much info here because it compromises BBLADES advantage over the competition. We have taught a lot of folks a lot of stuff. But as you long time viewers and participants know, we have been offering free technical information here for years since this forum began and will continue to share our 80 years of knowledge into the future.

Ok, your hull design and these props will decrease efficiency as they go faster which is opposite to most applications. The reason for this is a deep V of your vintage dose NOT want stern lift at 3/4 to WOT. Both of these props are doing that therefore increasing the drag on the hull. 4K to 4.5K is the sweet spot for efficiency and then the stern lift begins to hurt you. Also as the propeller gets nearer to the surface, depending on multiple bottom issues, aerated water will increase slip. Remember, these props are climbing to the surface.

I believe we can adjust your Bravo 1 propeller to be the better overall performer.


Brett

Brett-

Thanks for the response. Here the are results for the two props recalculating the Bravo slip numbers.

25 Bravo 1, Mercury Racing Lab Finish
RPMs/MPH/Slip
2500/29/27%
3000/36/24%
3500/44/20%
4000/54/14%
4500/60/16%
5200/66/20%

25 Hydro QIV Stock
RPMs/MPH/Slip
2500/30/24%
3000/37/22%
3500/47/15%
4000/55/13%
4500/61/14%
5000/67/15%

I tried spinning the hydro both out and in the speeds were almost the same in either direction other than at 3000 RPMs where I got 39 spinning in. I've yet to spin the Bravo's in to see how they perform. All of my speeds were with my Livorsi GPS speedo, however in chop I was able to get 68.5 with the Bravo using the SportsTracker app on my iPhone (speedo was in for repair this spring). So I need to do a bit more comparing before I decide what props to keep. At this point its going to be whatever ones feel better in Lake Michigan. On calm water I really can't tell any difference.

I just read your response in the other 292 post. It's good to know that the cup is flattened out on my props, that explains a few things such as the feeling that the Bravo's don't carry the bow as well, which is what I was really hoping for (more bow lift). As for your question on WTO of both- Bravo 5200 RPM's @ 66 and Hydro 5000 @ 67. I'll be in touch with you once I get some time call you.

Thanks
Mike

Brett-
Would you give me a call, I want to discuss the Bravo props. I left my number with your secretary, if you don't have it let me know and I'll give it to you again. Also the props are 24 castings.

Thanks
Mike

Mike,

I sent you a PM.

Brett