Ughhh...I'm under-propped

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cmattj
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Re: Ughhh...I'm under-propped

Post by cmattj »

I did the Bblades try and exchange but then you where purchasing them once the prop was right and tweaked..

I'm not sure now but BB may know their current program..

Only problem with cup is it can bring rpm down with no speed increases for top end but give you great cruising and holeshot.. duo props bite period..
My slip numbers are good and and seems yours are too.

Try before you buy would be great !

I'm with BB ..call Brett at b blades and at least have a chat with him.. it's a different animal with duo props!
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Re: Ughhh...I'm under-propped

Post by AsLan7 »

cmattj wrote: Thu Oct 19, 2017 8:19 pm I did the Bblades try and exchange but then you where purchasing them once the prop was right and tweaked..

I'm not sure now but BB may know their current program..

Only problem with cup is it can bring rpm down with no speed increases for top end but give you great cruising and holeshot.. duo props bite period..
My slip numbers are good and and seems yours are too.

Try before you buy would be great !

I'm with BB ..call Brett at b blades and at least have a chat with him.. it's a different animal with duo props!

.
Ok, roger that. I winterize tomorrow and the boat goes into hibernation Saturday. I'll put this on my short list in the spring. 8-)
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Re: Ughhh...I'm under-propped

Post by DMillerJD »

Hi All! I'm a new member here, and trying to get some prop-sizing info. I have a 2007 Cobalt 232, 496 Mag (not HO, 375 HP) with Bravo 3, 2.0 gear ratio, with 26p props. Boat was originally sold at and used only in Lake Tahoe (elev 6229). I live in the SF Bay Area, and have only had the chance to use it in Lake Berryessa and Folsom Lake (elev 450'). The first day I had it out (last October), I had 7 people on board, food, gear, skis, surf board and 2-person tube, great hole shot, top speed around 47-50 mph (based on iPhone) at around 4600-4800 rpm. WOT is 4800 rpm on this model. Won't be able to take it up to Tahoe until June or July, so still don't have data on how this boat as configured performs at altitude.

In talking with various people, was told too may different things to reconcile. The best I could glean was that 24p for low altitude would have been the "advised" pitch, and 28p for high altitude. But I have 26p, and don't really feel like buying TWO new sets of dual props!

Prior boat was a 2000 Cobalt 206, 5.0L Penta duo prop. Bought high altitude props, which it definitely needed given the smaller engine, and which I had the opportunity to do side-by-side comps on the props at high altitude.

I'm hoping some of you have practical experience with switching props on this boat. It's so dang easy to do that I'm willing to invest the money. Is there anyone out there who has run this boat/enginge/gear config with 30p at low altitude, 26p at high altitude?

Sorry for the long post! Thanks in advance for all your thoughts and experiences! (Can't figure out how to post pic to show her off!!)
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Re: Ughhh...I'm under-propped

Post by Big Block Power »

Ok matt and I replied to a exact same thread awhile ago. Same scenarios. I'm a bit confused at sea level your at almost 4800 wot? With 26 and max wot is 4800?
And you boat both sea level and high alt?
No matter what you will need two sets of props correct.
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Re: Ughhh...I'm under-propped

Post by cmattj »

Big Block Power wrote: Wed Apr 18, 2018 9:27 pm Ok matt and I replied to a exact same thread awhile ago. Same scenarios. I'm a bit confused at sea level your at almost 4800 wot? With 26 and max wot is 4800?
And you boat both sea level and high alt?
No matter what you will need two sets of props correct.
Late to the party. 1st off welcome from California too!! Nor Cal Delta!!

So Dmiller.. it would seem by your numbers your actually a sea level set up now as BB pointed out.
( That means it's sounds perfect unless it's banging off the rev limiter)

Get your gear ratio but the 26p is probably where you want to be..

Going higher in elevation reduces power so the lower pitch (24p) becomes more efficient but slower in top end as you already know.. A lot of my pals just suffer through a Tahoe boating day as it's not too frequent and the water temp never gets much above 60. But it is pretty

Right now you show 13 % prop slip which isn't great but not off either.

Go ahead to our new members section and introduce your awesome 232 and yourself to the crew!!
We love pics !!

And take a look at this thread.( one BB and I just touched on)

viewtopic.php?f=35&t=830&p=15945#p15945

It's a Delta boater with a simaler issue and his was optioned "high elevation option"

Welcome pal!!
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Re: Ughhh...I'm under-propped

Post by Big Block Power »

I agree with what matt is saying. Get a set of 24's for alt and go boating. You are where you need to be at sealevel. I'm not a huge fan of the merc b3 props. Hills bravo props are nice but not sure what you will gain. You might gain a bit better hole shot maybe a mph but that's hard too say. I had really bad luck with them on my Volvo.
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Re: Ughhh...I'm under-propped

Post by DMillerJD »

Thanks BBP and cmattj! Matt, you're brave being out on the Delta--I used to ski there with friends but was turned off by water quality and boater quality!

I actually think my prop set up is for Tahoe--that's where the boat was originally purchased. And topping out at 48-50 mph seems low. I'll have to check how she performs at Tahoe, and continue to gather data on prop slip as well. Didn't understand your comment about "get your gear"--gear ratio is 2.0. Even if she is under-propped at low elevation, I can't complain if I have people and gear on board and can still do 50. But thinking I might want to make some runs from Antioch to Sac (like for lunch jaunts), and would rather have the ability to really max out the performance. Guess I may just need to play around with options. Was hoping to just nail down something like, "Oh, you can go to 30 for the low elevation," and then just go find those used...Life is never that easy!
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Re: Ughhh...I'm under-propped

Post by cmattj »

DMillerJD wrote: Tue Apr 24, 2018 1:11 pm Thanks BBP and cmattj! Matt, you're brave being out on the Delta--I used to ski there with friends but was turned off by water quality and boater quality!
I hear you.. the 80's where a different time on the Delta.. but things have improved since then. Tahoe is beautiful but we like to swim in warm water, and the activities on the Delta are fun😎

Cmon that was funny!
DMillerJD wrote: Tue Apr 24, 2018 1:11 pm

I actually think my prop set up is for Tahoe--that's where the boat was originally purchased. And topping out at 48-50 mph seems low. I'll have to check how she performs at Tahoe, and continue to gather data on prop slip as well. Didn't understand your comment about "get your gear"--gear ratio is 2.0. Even if she is under-propped at low elevation, I can't complain if I have people and gear on board and can still do 50. But thinking I might want to make some runs from Antioch to Sac (like for lunch jaunts), and would rather have the ability to really max out the performance. Guess I may just need to play around with options. Was hoping to just nail down something like, "Oh, you can go to 30 for the low elevation," and then just go find those used...Life is never that easy!
Your close on your set up. But when you mentioned your only getting 4600 rpm to 4800 I felt your not seeing the rev limiter yet.

Most 496 ( 375hp) vs 496ho would most likely have a 1.81 gear Or the 2.2 for high elevation. So maybe some already put a 26p on it?

It shows a 24p was stock so maybe run the serial number to see if it's actually a 2.2?



By trying a steeper raked prop you'll add a lower overall effective ratio but it can now struggle because the blade angle is so steep. ( gets sluggish ) you don't have the power to pull it.

28p are a realistic option ( available)but I would make sure you can achieve maximum rpm now ( you should be able to feel the rpm limiter after holding wide open for just under a minute and trimmed) with the current combo.

Here is a Cobalt sheet from your model. Or you can call Cobalt to see how she was built for its destination.

Make another outing then we'll go prop shopping!
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Re: Ughhh...I'm under-propped

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DMillerJD wrote: Tue Apr 24, 2018 1:11 pm

But thinking I might want to make some runs from Antioch to Sac (like for lunch jaunts), and would rather have the ability to really max out the performance. Guess I may just need to play around with options. Was hoping to just nail down something like, "Oh, you can go to 30 for the low elevation," and then just go find those used...Life is never that easy!
Just checking in to see what you came up with? A lot of prop talk going on these days.
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Re: Ughhh...I'm under-propped

Post by Big Block Power »

Hey Matt are you still glowing from being in that delta. Alien Matt!!! Lmao
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Re: Ughhh...I'm under-propped

Post by cmattj »

Big Block Power wrote: Mon Apr 30, 2018 7:58 pm Hey Matt are you still glowing from being in that delta. Alien Matt!!! Lmao
Everyone knows You don't glow from high mercury levels in the water .. geeeze.

You just start craving 80s disco music and polyester . :shock: :mrgreen:
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Re: Ughhh...I'm under-propped

Post by Big Block Power »

cmattj wrote: Mon Apr 30, 2018 8:27 pm
Big Block Power wrote: Mon Apr 30, 2018 7:58 pm Hey Matt are you still glowing from being in that delta. Alien Matt!!! Lmao
Everyone knows You don't glow from high mercury levels in the water .. geeeze.

You just start craving 80s disco music and polyester . :shock: :mrgreen:
That's awesome. Your delta must be like our paper mill infested pcb polluted water here. We have lots of two headed fish.
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Re: Ughhh...I'm under-propped

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Big Block Power wrote: Mon Apr 30, 2018 8:37 pm
That's awesome. Your delta must be like our paper mill infested pcb polluted water here. We have lots of two headed fish.
Killin me!! As I explain to my grandkids... " no that's not a flounder, and fish are only supposed to have 2 eyes.
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Re: Ughhh...I'm under-propped

Post by Big Block Power »

Flounder wasn't he in a movie?
Called
Where the Delta meets the Pcb's
Ok Animal House!
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Re: Ughhh...I'm under-propped

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