That makes no sense. He hasn't even begun to work on his setup yet and just threw it on there...has barely ran the prop once. Already you can tell the prop is not right? Is that how you normally do things?Originally Posted by mdtritn21
That makes no sense. He hasn't even begun to work on his setup yet and just threw it on there...has barely ran the prop once. Already you can tell the prop is not right? Is that how you normally do things?
96 Bullet 20cc, Yamaha OX 250+, 10" jack, labbed 30" Bravo LH w/1.25" exhaust pipes, counter rotating Bob's lower, it goes faster when you spin it the other way...
He's already turning 5800 rpm's at 68 and the prop is slipping at 18% which is high for a Bravo. That prop is a 24" cupped to 25.5 but it's still a 24" prop at the root. If he can turn it 6000 rpm's it still only going to go 70 and slip real bad without some work.
So are you saying that a cup large enough to effectively raise pitch an entire 1.5 inches (which would be a sizeable cup) is slipping 18%? Does that sound right to you...since adding a cup that large would reduce slip quite a bit? Also consider that his lower unit is buried pretty deep at 3.5 inches. I'm not getting the same 18% slip calculation that you are...I'm getting a slip closer to the standard of 10%...just a few tenths higher actually. If he starts to raise the motor up the rpms will come up. I calculate that 6000 rpm will be reachable as lower unit drag and blade drag are reduced and also a speed of 70-71 will also be reached. The torquemaster can still get sufficient water at 1" below ptp and he's currently a full 2.5 inches below that and still running 68. Low 70's can easily be had when the motor comes up...
96 Bullet 20cc, Yamaha OX 250+, 10" jack, labbed 30" Bravo LH w/1.25" exhaust pipes, counter rotating Bob's lower, it goes faster when you spin it the other way...
That's a 201 and I'll bet it won't run at 1" under pad. If his raises it to 2.5 under he should get to 6000 rpm's but that prop will still be slipping.
I would bet right along with you that it won't run well at 1" below but it will run at 2.5" below all day long and maybe even as high as 1.5-2" below with the larger diameter Bravo on there and all that "high slipping cup" on it like you say. So the motor can go up another 1-1.5 inches and possibly even as high as up to 2 more inches. How much more speed do you think that's good for?
96 Bullet 20cc, Yamaha OX 250+, 10" jack, labbed 30" Bravo LH w/1.25" exhaust pipes, counter rotating Bob's lower, it goes faster when you spin it the other way...
As I said before if the prop wasn't slipping he'd be over 70 now so I don't know if he'll gain much speed at all. Start raising it 1/4" at a time and see when happens.
I always heard the Bravo XS requires u to pitch up. 25 Fury is stiffer then a 25p Bravo.
Bryan McDonough
2023 Nitro Z21 XL
Nitro Team
That's my experience with them too...about 1 pitch lighter than advertised from most other Merc props. Only other one I can think of that is also not quite as advertised is the Promax...but it is actually a tad stiffer than the pitch number given by Merc.
96 Bullet 20cc, Yamaha OX 250+, 10" jack, labbed 30" Bravo LH w/1.25" exhaust pipes, counter rotating Bob's lower, it goes faster when you spin it the other way...
I just have never seen or heard of a cupped Bravo, without a blade missing, slipping anywhere near 18% so I was trying to figure out how you got that number...had all kinds of trouble calculating anywhere near that. But like you say...we'll see what happens.
96 Bullet 20cc, Yamaha OX 250+, 10" jack, labbed 30" Bravo LH w/1.25" exhaust pipes, counter rotating Bob's lower, it goes faster when you spin it the other way...
Not that way on my boat. 24 fury and 24 Bravo xs both run 5800. Mine might be the oddball though.
That's why I said earlier that he might need a true 26" bravo and not a cupped 25.5" which is a 24" prop. Mercury says go up 2" in pitch when going from a fury to a bravo xs but I also said buy the prop try it and if it doesn't work sell it and buy a 26".
Are those running at the same prop height? The bravo will run higher than that fury will for sure.
This is some interesting conversations going on here. When I went to a Bravo I text Scott Reichow, who is the designer of the prop for Mercury Racing. I asked him about the slip that I was getting, 60mph at 5000 rpms = 18%. He told me that since Bravo XS run light on pitch I should be inputting 26" instead of 27", which what my prop is. That worked out to 14% and he said that at slower speeds will always have more slip. 3 blade Fury run heavy in pitch , Tempest run correct, and Bravo's run light. He said if moving from a Fury 25' that I would need a 27" for the same rpm's. you can see all kinds of question on the Mercury Racing website, pull down the blog and read the story Dial-in to the XS. at the end of it is where people had sent in questions and Scott answered them. Hope this helps.
BuddyT
I’ve moved them all over the place, but when I get more rpms out of the Bravo my steering gets too stiff to turn. I’m starting to think I have a motor issue since I have run a bunch of props and all the max rpms I get are very close.
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