25 Tantrum 28 Bravo 1
 

Are there any Tantrum guys running a 28 pitch stock Bravo 1 4 blade prop with stock HP500 motor or similar HP, if so what do you think of it? How many RPMs are ya turning?

good question..i'm looking to try a few different prop options.

I have a solid hub B1 28 that I used to run before I recently upgraded to a XR w/ big shaft. I could turn it 5300. but that is with an Extension box. i am pretty sure that this was the prop that was used back in the day when the boat was raced with the HP500. It has not been labbed but it has had something done to it... Its fast. I could turn it 100 more rpm than a stock b1 26. Explain that...

Ok following a lil test and tune day here's basically what I found. Looks like I run bout 15% slip at 5200 with more like 25% at lower rpms like 3000. I tested a standard 26 Bravo 1 and ran 72, used a BBlades 26 Bravo 1 and ran 72 except I am sure I had a some speed left but the boat was umm lets call it loose, I also had a 28 Bravo 1 that has been beat on and cup added and ran 69 but this was at bout 4700 and could not get the boat loose whatsoever. The 28 gave just about 10 mph more per given rpm vs the 26's and I really like the 50's at 3300. I'm confident the 28 was just giving too much stern lift or lack of bow lift whichever way ya wanna say it but that only seemed to develop at near max speeds at lower speeds the boat handled similar to the 26's per given mph. Anyways, so I'm thinking maybe a standard 28 or maybe a BBlades 28 with a lil bow lifting tweak might get me middle upper 70's, but that's probably a lil wishful thinkin too.

Oh water conditions were basically smooth as smooth gets on a lil inland lake. Nothing really unexpected and nothing the prop calculators wouldn't have told me, but figured I'd share. I wasn't initially expecting the high slip #'s at lower rpm's but after a bit of studying/research the propeller design stuff makes sense.

Oh I almost forgot, not that its laboratory accurate but my Garman GPS and my in dash non GPS Gaffrig were within a mph across the range so I am very pleased with the Gaffrig.

Before I rebuilt my engine, I was running a Throttle Up labbed 28 Bravo 1 at 5300 and boat usually ran around 79 to 80 GPS. Back then boat had 555hp. Labbed 30 would run around 83 at 5250.

Along with the extra 100 rpm I got 2-3 mph with this 28' that I have. And it was less efficient than the stock 26 at cruz'n speeds. But Bad a$$ up top

Yeah, but its making the engine work harder at that rpm, like going up a bigger hill in your truck. You still have to push the throttle forward just as far to run 3300rpms with the 28 as you would running the 26 at 3700rpms.

WOW you only droped 50 rpms from a labbed 28 to a labbed 30 how did you manage that. The normal drop would be 300-400- rpm drop. My old 25 was the smith bros race boat and with 500hp would run 74-76 with a 26 at 5250.

Thanks for the comments everyone, Griff's comments are making we wonder a bit bout how to get dyno curves for my HP 500 short of pullin it out. Anyone got data from maybe a rebuild or something on one as it seems factory data is a closely guarded secret ? I've also contacted BBlades searchin for their recommendations, so I'll keep ya posted with their thoughts.

There is a simple way to test.

Run the 28 at 3300rpms and mark where the throttle is with a piece of tape. Then run the 26 up to the same mark on the tape. If the throttle is in the same place, you are using the same amount of fuel. The rpms will be higher with 26 of course, but the engine is not loaded as much. The HP500 will make its best power all through the curve if you prop it to run at about 5200rpms.