How do they compare?

[mdtritn21]

If your running a Gen 2 lower you can get low slip numbers. I believe Don Weed said they were getting unbelievably low slip numbers with a Gen 2 lower after it first came out down in the 5% range. I still think a Pro max of the right pitch would get you 90.

[rocketman6965]

Yeah MD. I just don't know how they run as far as stiffness. I am getting 3% slip from 27 Fury or 12% from the 30 Bravo so do I try a 28 hoping it is more efficient than Bravo or a 29 to make up for an undetermined slip number? I have a 29TXP OT4 coming. Won't be able to run until late January on account of vacation and club tournament as soon as I return. Will post numbers then

[headhigh]

fishnfireman thanks for clarifying. You are still invited. Not to prove anybody wrong. Let's go fishing! LOL I like what JRisco posted. When I bought 300 from great guy in Lake City, FL, it came with a Gen2. He flat out said with the utmost conviction, RUN A 27 FURY. So I got lucky on BBC and found a new one in the box for a great price. The 30 Bravo, I absolutely knew the history of prop. Bought originally by fellow BBC'er I contact often in Jacksonville then sold to a guy who ran it once. Completely stock prop. I don't know how it does what it does but it did. LOL x 3. As far as prop slip and I hope this doesn't go too long. When I sold Robalo fishing boats with my dad in the 70's and 80's, I made up my own formula for slip calculator without outside input and discerned after calculation you needed to allow for "slip". Here is example 6000 RPM's, 1.75(.571) gears, 27" pitch for you math junkies:
Flywheel RPM's (6000) x Propshaft RPM (.571)=3426 prop shaft RPM's
Prop shaft RPM's (3426) x prop pitch in inches (27)=92,502 inches per minute!
Inches per minute (92,502) divided by 12=7,708.5 FEET per minute
Feet per minute (7708.5) divided by feet in a mile (5280)=1.4599 miles per minute
Miles per minute (1.4599) x minutes in hour (60)=87.59 MILES PER HOUR with 0 slip
Based on Croxton advise to add an inch of pitch the formula would equal 90.84 MPH or 3.13% slip. Again this is just the math and "many variables" for actual prop but I can say ALL the Bravos I've run on all 3 motors had similar slip numbers (12%) And that is the skinny gents

I think you forgot to factor in the coefficient of thermal expansion of stainless steel (or X7 alloy for the Fury), as well as the short term effects of global warming. Other than that, you’ve got it covered.

[rocketman6965]

You're almost there. You forgot curvature of the earth and whether it is salt or fresh water density.

I think you forgot to factor in the coefficient of thermal expansion of stainless steel (or X7 alloy for the Fury), as well as the short term effects of global warming. Other than that, you’ve got it covered.

[mdtritn21]

You forgot to figure in the density of cold water helping you drop slip numbers because every one knows cold water gives a prop something harder to push against.

[D-wayne]

To me it is interesting that you are sticking with mass production propellers. I was always told that a great marine machinest can tune the props to bring out the most performance from them. The boat and weight distribution has a lot to do with the top end speed and yet I do not see any discussion about how you changed set ups and the outcome.
With all the different types of props it would be interesting to see the performance data, start midspeed top end ....
Good luck with the quest.

[Bassin Bob71]

To the OP, I'm genuinely curious how the boat handles those speeds? Not sure I'd have the stones to drive it To 90....

[rocketman6965]

D-wayne thanks for your insight. The stock Fury is obviously dialed in but maybe if I'd had sent the Bravo to Mark with my detailed setup, he could've tweaked for better slip numbers.

Bassin Bob it is a thrill! It felt great. I believe adrenaline and experience take over. I wasn't even aware of making steering corrections.

[jrspop]

Joe, I ran a labbed 30 Bravo today, the one with the bell, someone cut 4 big holes, at least 1 1/4". 82.7 close to 6000. Pretty good load. I find Bravo's run at least one pitch down. My 27 trophy has run faster, but I need to run it with the load I had today. I'm not sure a Bravo will ever be the fastest on our boats, but this prop is close. The 2 fastest props on my rig are labbed. I will eventually get a promax, just undecided about pitch. MD says 27 p promax spins 100 rpms less than 27 trophy. Mercury racing confirmed that. Glenn Reynolds at Reynolds Racing said either a 26 for load or 28 for speed on my rig. You can run them higher as well, a big plus.

[rocketman6965]

Thanks Keith. Good to know. Looks like even a labbed Bravo has a lot of slip for our boats. Your worked 27 Trophy is faster than 30 Bravo so far.

My stock 30 Bravo ran 86.5 at 6070. Tourney loaded 1/2 tank fuel.

[mdtritn21]

I'm turning the 27" trophy 5750 at 78.6 mph and the 27" pro max 5650 at 77.6 mph and feel pretty good since it's an old 225 efi but it's a 2004 TR21 which is the model that's actually 21'. The Pro max 27" is actually a 28" pitched down to a 27" and I think that's why it's harder for me to turn. I don't think Joe would have any trouble turning a 28 or even a 29 because you can run it higher than a trophy. I always figure a Bravo at 12% because they are low in pitch and don't add the extra 1" for SS props in the calculator.

[rocketman6965]

Thanks MD. That gives me a good idea. Anyone willing to lend me 28-29 Pro Max? I'll pay shipping both ways obviously and agree to compensation should anything happen to it.

Just edited to say 29TXP on the way may also do it. Will wait for results first.

[ldbass55]

Good luck chasin that number Joe, hope you get there...I do get a chuckle out of some of these guys and their prop slip figures...I really dont know if you can ever get a real number on actual prop slip..There are way too many variables that have to be figured in..added cupping changes pitch calculation..so does the fact that a 29 bravo is not a true 29 pitch, and a 29 promax is actually a 30 pitch, not to mention the fact that stock merc props rarely come out of the box the same...the slip calculator is just a tool, the bottom line is GPS speed...
LD

[rocketman6965]

Yeah LD. Thanks for encouraging words. I'm really excited to receive the TXP29. If it runs as stiff as the Fury but can be raised higher than a Trophy, I believe it's doable

[mdtritn21]

You can run a tempest higher than a trophy so it should run higher too.