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View Full Version : hp limit on a stock bravo I drive



DonZi 26
10-06-2010, 04:13 PM
ok lets talk.....

whats the outmost max hp that a stock bravo I drive can handle ??

i've heard some say that they have over 700hp with a stock bravo I and run smoothly, but take very good care of it....

what you think guys ?

Donziweasel
10-06-2010, 04:24 PM
rated by Merc for 400, but can take way more than that. It is more about how the drive is treated and how you drive the boat than it's rating.

Carl C
10-06-2010, 09:02 PM
Mine lasted several seasons running hard with the 496 HO. The 525 EFI broke it in 7 hours...:nilly:. The XR/Imco shorty has now lasted 2 seasons.

BlownCrewCab
10-06-2010, 09:04 PM
We have done 650hp and raced it (offshore) for a year or more. Yes you need to be consious of prop speed when the prop is going in and out of the water allot. The newer Props make it harder on the drive since the props bite so well. (example) your drive will last longer with a 3 blade than a 4 blade since a 3 blade doesnt bite as much.

The Hedgehog
10-06-2010, 10:56 PM
Ran 600 or so through one for a couple of seasons. No problem. It never broke

osur866
10-07-2010, 12:47 AM
I'm hoping mine will handle, just shy of 600 HP, think it not only depends on how easy you are on the sticks but also the weight of the boat, 600 HP in front of a Bravo in a 2800lb boat I think will live alot longer than the same HP in say a 6000lb boat driven the same. Steve

Dr. David Fleming
10-07-2010, 02:20 AM
Good question about Bravo I strength. I notice the Bravo appears in Merc advertising in 1988 after a year or so of 454 Big Blocks built with the Alpha drive. Then it runs through production to today - that is a long time!

Looking at several of these drives I see some advertised variations -
"Bravo I" and "Bravo I Performance" are two of them. Some Bravo I drives have water pickups on the sides of the lower and use an "ear muff" water hook up, and some have water intake in the bullet nose and use a "muff" water hook up.

All these drives equal in strength? and performance? Boat mechanics seem to consider them the same. Examination of the repair manual shows many special tools and a fairly advanced procedure.

My effort to get Tyler Crockett to talk about Bravo I resulted in his opinion of it as a "fast" drive through the water for stock 400 - 500 hp engines - with need to limit the prop loading on it.

He had a real beauty all tore up when someone in an alcoholic induced stupor revved up his Whipple charged 502 to about 5000 rpm and then decided to drop it in gear - twisted the U joints all apart shattered the bevel gears - yah! even though it drives into water you can't pull a hole shot like that.

osur866
10-07-2010, 04:55 AM
Side note, I'd say not all Bravo's are equal, I've been told the newer "Swept Back" Bravo's use the same upper gear set as the Bravo X drive only difference between the X and reg. Bravo is the top cap in the X has a steel tower. I know a cpl people pushing 600-700 Hp thru a standard Bravo without problems, and then again I've also heard of a few tearing up XZ's and XR's with less than 525hp so, I still think it comes down to a combo of things, how it's driven, weight of boat, and if your using 3, 4, or 5 blade props. My .02

The Hedgehog
10-07-2010, 06:34 AM
I'm hoping mine will handle, just shy of 600 HP, think it not only depends on how easy you are on the sticks but also the weight of the boat, 600 HP in front of a Bravo in a 2800lb boat I think will live alot longer than the same HP in say a 6000lb boat driven the same. Steve

Unless you are one of those that spends more time above the water than actually in the water:pimp: I heard that you drove it like you stole it around LOTO on Shootout Weekend. The guys from Nashville were pretty impressed.:pimp:

osur866
10-07-2010, 06:52 AM
Unless you are one of those that spends more time above the water than actually in the water:pimp: I heard that you drove it like you stole it around LOTO on Shootout Weekend. The guys from Nashville were pretty impressed.:pimp:
Well Bill you will need to see first hand next year ;)

VetteLT193
10-07-2010, 12:53 PM
It is mainly going to end up in how you run the boat. If you like to run hard, fast, and long... it won't last long so get a better drive. If you are gentle on it no problem.

DonZi 26
10-07-2010, 02:09 PM
ok how im gonna run over 600hp on a stock bravo 1.......


boat is a donzi 26zx and they say it weighs about 5800lbs...

now we'll see how it goes hopefully it will last long enough, it has less than 150hrs on it....

mike o
10-07-2010, 09:17 PM
I'm hoping mine will handle, just shy of 600 HP, think it not only depends on how easy you are on the sticks but also the weight of the boat, 600 HP in front of a Bravo in a 2800lb boat I think will live alot longer than the same HP in say a 6000lb boat driven the same. Steve Doing a little upgrading are ya.....:kingme:

osur866
10-08-2010, 12:32 AM
Maybe, we see. It's always a LONG winter ya know!

Dr. David Fleming
10-08-2010, 12:35 AM
Just ran across July 2010 Performance Boats article by Tyler Crockett,

"I wouldn't be worried about beefing up a Bravo to run behind a 650hp. You just need to take it easy getting up on plane and roll into the throttle easy when you accelerate, and you should be fine. One thing that is important when you do decide to rebuild a drive is that you have the steel tower machined into the upper case to suppoort the upper gear set. There are several tricks to building the drive, such as using the bigger prop shaft and treating the gears to make them stronger. Also, make sure you install a drive shower to help keep the upper cooler, as it is out of the water when you're running. They also have stud kits and stronger top caps to put on the drives too."

In another discussion Tyler talks about running 1000hp into a Bravo,

"We have built several Whipple 540s that made 950 to 1,000hp without any trouble...Your next issue will be the Bravo drive, and keeping it in one piece. We have had several customers running big power and torque on the Bravos, but their time has been limited. I have a customer with a 28 Eliminator and watched him go through three drives each summer - until we put a Imco SCX drive on. How he has run two seasons without a problem. He did loose about 2-3 mph with the bigger drive, but he gained reliability, which is a plus."

It would appear that the Bravo drive starts getting touchy with 650hp and is over its head at 950hp. Except for Carl C - 540hp for him! Also it would appear that a stock drive Bravo is fast.

Wonder how Tyler would rate one of his rebuilt Bravo drives with big prop shaft, heat treated gears and steel tower and cap with studs against a Bravo XR or the Imco SCX - 2-3 mph is significant to some.

Planetwarmer
10-08-2010, 12:44 AM
I wonder if all that work to a B-1 would cost more than an XR.

Dr. David Fleming
10-08-2010, 12:53 AM
Tyler didn't say it but I think he uses the diesel gear set which have the same ratios and a thicker center cross section but are interchangable.

BUIZILLA
10-08-2010, 07:21 AM
Dr..... is it possible you can go at least one post without pumping Tyler? is there ANYBODY else in this world you reach out to?

Carl C
10-08-2010, 09:14 AM
Donzi 26, I would run the Bravo and see how it goes for you. Maybe your driving techniques and waters will make you one of the lucky ones. Be sure to throttle back if the drive leaves the water. It's not always possible to do this though. If the drive breaks I would sell it for parts and upgrade to an XR. I found a brand new XR upper on OSO for $3,560. I paid about $3,000 for a very slightly used Imco shorty lower (it might have been less, I don't remember the exact cost). Good luck with your project and it would be cool if you document your project here.

The Hedgehog
10-08-2010, 11:37 AM
I wonder if all that work to a B-1 would cost more than an XR.

It would and still would not have the XR tower.

I would do like Carl said, run the standard for a while. You can spend $1,300 to upgrade the gears but I would spend that money on an XR. Or you can not destroy the Bravo I and sell it.

My Combo = XR that has been professionally setup, Max Billet Upper, IMCO lower and Billet Top Cap. Several folks from this area run that with upwards of 1,000 hp.

The Hedgehog
10-08-2010, 11:44 AM
Wonder how Tyler would rate one of his rebuilt Bravo drives with big prop shaft, heat treated gears and steel tower and cap with studs against a Bravo XR or the Imco SCX - 2-3 mph is significant to some.
__________________
Dr. d

Old news. Folks are now mating a SCX upper to standard SC lower. They hold together well and have BIG gears up top. No speed loss.

The weak link behind the XR is the gears. You can heat treat them, cryo them and do a special dance. In the end, torque will kill them anyway. We have found that it is better to go through the drive more often than do special treatments to gears. The SCX upper is far superior.

If your boat is really fast, 2-3 mph just a matter of guts and how long you can hold it at speed.

DonZi 26
10-08-2010, 01:04 PM
Yeah im hoping that at least i will last 1 season with stock drive then i would see next fall.....just bought a new 625hp engine and dont have the bucks for an XR drive...(you know what i mean guys)......

still my drive is suppose to be in excellent condition but that does not matter....

i will definately keep you guys posted and will upload some pics when i get them...im really exited for this new application, im hoping to get into the high 70's,

then we'll see...

hey carl wots ur top speed with that 525 ?

Carl C
10-08-2010, 01:56 PM
hey carl wots ur top speed with that 525 ?

Best recorded gps top speed to date is 85.8. That is hitting the rev limiter. I can hit around 83 any time I want. This is good enough for me as durability was a big concern for me over top speed.

How about pics of the new mill?

DonZi 26
10-08-2010, 02:13 PM
i havent got any pics of the new engine as yet....but will surely post them when i got them....

here's my previous stock 502 carb....hope you like it bud....

The Hedgehog
10-08-2010, 04:25 PM
i havent got any pics of the new engine as yet....but will surely post them when i got them....

here's my previous stock 502 carb....hope you like it bud....

pretty

DonZi 26
10-08-2010, 04:32 PM
thanks bill......what about yours have you got any pics ?

Carl C
10-08-2010, 04:55 PM
Looks good. I'd recommend an Imco -2" shorty lower. You will like it and if you blow the drive you're only looking at buying a new upper.

The Hedgehog
10-08-2010, 05:04 PM
thanks bill......what about yours have you got any pics ?

It won't let me post them again. Look over at the show us your engine thread. There is a link with a bunch of my pics.