I have a bravo one labbed 32p prop that I beleave was worked from merc racing. The 34p I purchased used with is also labbed. The 32p has cup built only into the rounded tail of the blade, as the 34p has a little cup built into almost the entire blade from the beginning all the way up and around the tail. What will the 34 perform like over the 32 ?? With all that extra cup give more bow lift or more stern lift ??

I cant speak to how the boat will handle one prop vs the other. What I can tell you is the 34 Bravo has a design flaw straight from Mercury and is a poor performing prop. I know from experience with my old boat. The 32 and 36 are good props

Can you explain this a bit more? I am running 34's right now. What flaws and affected performance how so? I am on the limiters now with 34's and from research have noticed excessive stern lift complaints from the 36's hence why I have not moved up....

The 34 Bravo is simply a poor performing prop compared to the 32 and 36. The 34 accentuated the porpoise in my old 33 Daytona from 90-110 where the 32 and 36 the porpoise was not as bad. The 34 also had a real loose feel where the 32 and 36 felt hooked up. I know others like Teague have also experienced the same. I usually ran 36's on my 33 Daytona and they were great props, slipped a little getting on plane but otherwise did everything right.

I believe I have written volumes on this on this forum over the years. If one was to search I believe you will find it. Due time constraints I will offer some shortened history.

I was at Mercury racing during our development of the 34 Bravo 1 propeller. This was our first larger pitch Bravo 1 post 6ish years of Bravo 1 props only going up to 30 pitch. The 34 was the first and only 1of 2 propellers that are actually 15.25" in diameter. The current 34 was intended to be our 32 pitch casting but due to the actual pitch of the rest of the family we remarked it as the 34. This information is history but is not the reason for the performance issues.

The 34 Bravo 1 is actually a wonderful propeller. The negative feedback is mostly do to the propellers lack of ability to plane easily on many applications. The reason for this is the flat pitch progression at the 70-90% radial arcs. In other words it is flat in that area. The water slips off the blades...... The good news is we can fix this on most applications.
If you plane well with this prop and you can pull it, it is historically a fast propeller. That's the skinny in a nut shell. Yeah there was a bunch more to the story but this is the most important stuff and the rest is just Mercury behind doors stuff and I don't need to bore you.

History class closed for the day.........gotta meeting to attend.

Have great weekend people!

Brett

So besides talking about the 32,34 & 36 can anyone answer my ?? about the cup difference on the 2 props that I got ????????

I have a 32 and 34 both lab finished for my boat from merc. For some reason the 32 seems to lift the stern better which really helps my boat on the big end (28' profile cat). What kind of hull was the 34 labbed for? I would think a stepped hull or cat due to the tall pitch...not a lot of straight Vs out there pulling that big of wheel. So, it should be a stern lifter, which is what most cats like.

The only way to know is to try it...I like to try any prop you can get my hands on.

Years ago we only Labbed to the standard spec. recipe.
BBLADES Labs specific to the boat and owners goals. We/BBLADES started that process and now others do it or attempt to do it too. I'm not trying to sound cocky, it's just a matter of fact that we have been adjusting Lab recipes for years when others were only blueprinting props. Varying recipes are performed at Mercury Racing to some extent but not as aggressive as we do. Dennis and I did adjust recipes a decade ago at Merc Racing but again it was less in-depth.

To that end, it be impossible to determine the specifics of Dave269's cup variations without seeing the props. So, to answer your question, the cups were adjusted for a specific reason or boat or some one adjusted them without knowing what they were doing. Second reason is most likely.

Brett

I just got this boat together this year and only had it out twice, I really have to get adjusted as this is my first cat w/ 890hp. I ordered a memory box for my tach & my speedo also has recall. Just don't have time to stare a the tach @ 100mph. I only have ran the 32p but I'm on the rev limiter and the boat started to porpoise so I backed out of it. Brett, I'll do my testing and record my results w/ both props before I call you. Thanks for the feedback guys !!!

Hi Dave,

I would like to attempt to answer your questions on the cupping differences on your 32 and 34 Bravo 1's. The cupping on the 32's around the tips only will generate more bow lift. The fact that there was none at the trailing edges is an indication the that even more bow lift was needed. Trailing edge cup provides more tail lift, while tip cup generates more bow lift.To eliminate the tail lifting cup at the trailing edges, and adding cup around the tips is a recipe for bow lift. Your 34's have cupping at trailing edges , but not around the tips. This creates tail lift.

We must also consider the pitch in determining bow/tail lift. The higher pitch props turn less rpm. Therefore the WOT torque output is higher at the lower rpm. You can verify this by looking at a dyno sheet on a motor. The added torque exacerbates the lift characteristics of the propeller. So if you run the tail lifting Bravo 34's, the tail lift will increase even more, due to the higher torque at the lower rpm. The 32's are bow lifters, and turn higher rpm which exacerbates the bow lift even more. So there are 2 things going on at the same time. Cup differences and rpm changes due to pitch.

We must also consider rake angle as to it's effect on lift. High rake props lift the bow more than low rake props. However, I assume the rake angle is similar on both your 32's & 34's

We at Hydromotive first look at the application to determine what lift characteristics are needed. Then we select the correct prop for that application. More often than not, we then make changes to that propeller to dial prop in specifically. Also, we have both bow & tail lifting 4 blades, and bow & tail lifting 5 blades. This allows us to dial you in with box stock props more easily. We also build all our props in every inch of pitch.

Thanks,

Thom