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View Full Version : Anybody have expierence with this?



scarabrick2
09-03-2005, 08:03 AM
Saw this in the outdrive forum and was thinking it might get better attention over here.
Whipple Vs. Bravo 1
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I just recently purchased a 1999 270 hallett with a 502efi/Whipple. I already installed the biggest O.D. pulley for the whipple, so the super charger boost would be decreased. However, my question is how much boost can the outdrive handle out of the hole. The original owner has stated 600+hp comes from the motor and I realize thats working the outdrive hard. The outdrive was sent to the Bravo shop for oversize bearing and was serviced 3 years ago.
My wife wants to go wakeboarding/sking and I feel uncomfortable hitting the thottle hard even with a 22 four blade pitch prop and putting 5 pounds a boost out of the hole. What can the Bravo 1 handle?????
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Vegas Hallett

BADBLOWN572
09-03-2005, 08:08 AM
That is a question that is difficult to answer. What I have found with blower boats is that if you roll into it slowly, you will be fine. I know on my boat when I pull a wakeboarder I usually take off around 2200rpm. The boost is not an issue at all. I know guys with a N/A motor that will snap drives of of the line. You need to take off so the boat can catch up to the prop speed and not just hammer it out of the hole.
You have to remember that an XR bravo is bult for around 500h.p. Mercury is using them on their new 600SCI, but that is about the max that you can do safely. H.P. doesn't kill the drives it is the torque. If you are putting a lot of torque on your drive when you take off, you will kill it. If you roll into it slowly, you should be fine.
Using your boost as a reference point is a bad idea. I would watch RPM and stay below 3k RPM until the boat rolls over because that is typically peak torque on the drive.
If you stab it off of the line, it would be like dumping the clutch on a car. If it bites, you will have a lot of stress on the drive train or you will simply blow out the prop and cause a lot of stress as well. Bravos don't like a lot of stress or they end up in a million pieces. TRUST ME!!!!

Sane Asylum
09-03-2005, 08:16 AM
That is a question that is difficult to answer. What I have found with blower boats is that if you roll into it slowly, you will be fine. I know on my boat when I pull a wakeboarder I usually take off around 2200rpm. The boost is not an issue at all. I know guys with a N/A motor that will snap drives of of the line. You need to take off so the boat can catch up to the prop speed and not just hammer it out of the hole.
You have to remember that an XR bravo is bult for around 500h.p. Mercury is using them on their new 600SCI, but that is about the max that you can do safely. H.P. doesn't kill the drives it is the torque. If you are putting a lot of torque on your drive when you take off, you will kill it. If you roll into it slowly, you should be fine.
Using your boost as a reference point is a bad idea. I would watch RPM and stay below 3k RPM until the boat rolls over because that is typically peak torque on the drive.
If you stab it off of the line, it would be like dumping the clutch on a car. If it bites, you will have a lot of stress on the drive train or you will simply blow out the prop and cause a lot of stress as well. Bravos don't like a lot of stress or they end up in a million pieces. TRUST ME!!!!
What he said........ :frown:

scarabrick2
09-03-2005, 10:09 AM
top.
more info please

BADBLOWN572
09-03-2005, 10:26 AM
top.
more info please
There really is no more info to give. If you hammer the boat out of the hole, you stand a good chance to blow up your outdrive. It was not designed to hold the type of power that you are throwing at it.

dirty old man
09-03-2005, 10:28 AM
Bad Blown sounds like an experienced guy. His advise is right on. Keep the pitch low, and ROLL on the throttle, na or blown. Don't use the same prop for wake boarding and top end runs

Miss Perfect
09-03-2005, 10:28 AM
top.
more info please
Geez... what do you think this is? A boating forum or something? :D

BADBLOWN572
09-03-2005, 10:35 AM
I will make this very simple for you.
Look at the graph that is found on the Whipple website. You increased your torque by over 300 ft/lbs and your H.P. over 250 h.p. If you think that stuff doesn't break at the increased #'s you put on, you are crazy. Again, the drive was designed for 500h.p. and less than 500 ft/lbs of torque.
If you stab it off of the line, you are nutts. With your setup you get peak torque somewhere below 2800 RPM. If you don't come in to it slowly, you will grenade your outdrive very quickly.
Don't reference boost. Reference your RPM and learn about your engine and boat. If your RPMs are higher and the boat is trying to catch up quickly, you will blow more cash repairing your stuff than a crack ho on welfare day. Again, just roll in to it slowly and you will be fine.
http://www.whipplesuperchargers.com/Images/productimages/500hpefigraph.jpg

BADBLOWN572
09-03-2005, 10:37 AM
Bad Blown sounds like an experienced guy. His advise is right on. Keep the pitch low, and ROLL on the throttle, na or blown. Don't use the same prop for wake boarding and top end runs
Exactly. If you want to go skiing, I would step down somewhere around 1-2 prop sizes. This will give you a better hole shot and put less stress on the drives. Think about it this way, would you take off in 3rd gear in your car? You might get more top end numbers in 3rd gear, but it will really put some stress on your tranny.

BajaMike
09-03-2005, 10:57 AM
Exactly. If you want to go skiing, I would step down somewhere around 1-2 prop sizes. This will give you a better hole shot and put less stress on the drives. Think about it this way, would you take off in 3rd gear in your car? You might get more top end numbers in 3rd gear, but it will really put some stress on your tranny.
I agree...get aluminum 20 pitch, 3 blade prop...not expensive...and use it just for wakeboarding-skiing. The aluminum flexes a little, reducing the strain on your outdrive.
Also, be sure you don't over-rev your engine with the 20 pitch prop!

scarabrick2
09-03-2005, 11:49 AM
Thanks for the great info!!!!
Here's what he has:
The speed prop my bro has is a 28 4 blade labbed. Also has a 26 4 blade labbed and a 22 4 blade labbed. We ran the 28 and hit 77 ish on gps with trim neutral ,no tabs. ran the 26 70 ish Were going to put on the 22 and keep it on for slow cruising hopefeully better fuel ecomony and skiing/wake boarding. I think this small pitch prop should be easier on all of the equipment. I do like teh small alum prop idea. Might have to get us one off of e bay
Rick

VegasHallett
09-03-2005, 12:03 PM
Bad Blown 572: Thanks for the info that's kinda what I thought would happen. I guess this winter I need to either upgrade the drive or have some serious work done. I know every mechanical system engineered has a weak spot but my outdrive is way out of line. What is beeter a XR drive or take the Bravo 1 to reputable shop and have it upgraded more? Either way I still will never hit it out of the hole hard. I just don't trust my Bravo 1 without knowing the runtime history (530hrs) from the previous owner.
Thanks

dirty old man
09-03-2005, 12:20 PM
Vegas Hallett, you are the luckiest guy in boating - 530 hours on a Bravo? You are so far ahead you've got money in the bank

VegasHallett
09-03-2005, 12:52 PM
I just purchased the boat two weeks ago (532hrs) and the bravo was rebuilt three years ago (Bravo shop). I figure the outdrive has 250 hrs since the rebuild. That's not too bad for the unit.

BADBLOWN572
09-03-2005, 01:03 PM
Thanks for the great info!!!!
Here's what he has:
The speed prop my bro has is a 28 4 blade labbed. Also has a 26 4 blade labbed and a 22 4 blade labbed. We ran the 28 and hit 77 ish on gps with trim neutral ,no tabs. ran the 26 70 ish Were going to put on the 22 and keep it on for slow cruising hopefeully better fuel ecomony and skiing/wake boarding. I think this small pitch prop should be easier on all of the equipment. I do like teh small alum prop idea. Might have to get us one off of e bay
Rick
If you go with a smaller prop, you will actually sacrifice fuel economy. To get to the same speed, you have to spin more RPM's and that sucks up more fuel. Motor works a little harder, but save the outdrive. As long as you are not spinning the motor to around 6k for cruising it won't be bad. For cruising I use a top end prop for long drives. For me 65mph is right at 3200 RPM. Can cruise at 65-80 without really working the engine. Fuel consumption goes down too. (again think of it as a car. Would you rather drive to the river in 1st gear or 5th gear)
What RPM's are you spinning at top end. Sounds like a pretty steap drop off between the 26 and 28 pitch prop. If you can spin the 28 to the limiter, I would check and see if you can spin a 30 and if you cant, maybe lab a 30 and you will get extra out of it.
Bad Blown 572: I know every mechanical system engineered has a weak spot but my outdrive is way out of line. What is beeter a XR drive or take the Bravo 1 to reputable shop and have it upgraded more?
Thanks
That right there is the million dollar question. I have broken stock XR's, Upgraded, B-Max'es, etc... The only thing that I know people have had good luck with is the Max Machine drive. My feeling is that any shiftable drive will break under the wrong circumstances. Some feel that if you upgrade the shafts and gears over stock, you shift the weakest point to the cone clutches, couplers, and casing. I really don't know. Any way you look at it, you are running a drive not designed for that type of power. However, if you have 530 hours on the drive, I would just keep changing the oil in the drive and don't touch it. I feel, if it aint broken, why fix it. If you start draining your oil and it looks like glitter, that is the time to tear into it. You can also see metal shavings on the magnetic tip of the drain plug. With a motor like yours, I would change your drive oil every 10-30 hours. Cheap insurance that your drive will live.
BB572

burtandnancy
09-03-2005, 02:51 PM
Bad Blown, going to humbly and slightly disagree with you in regards to loosing fuel economy in the higher rpm range. Hull design, efficiency and weight all come into play here. A big block under heavy load will certainly use more fuel than a small block running a light load at even 1,000 rpm's or more. Other than that, I think you're pretty close. BTW, I had a dually once that I pulled the 4.10's out of to go to 4.56's. The same loads, same trips, but a few hundred more rev's and I got better mileage. Didn't have a vacuum/boost guage but wish I had.