Bravo III drives

[96 Arriva]

I have recently purchased a modifed Arriva (by Bayliner) the boat now has a new marine 454 in it, and makes in excess of 450+ hp - currently there is a bravo 3 leg on with 26 degree props - I'm looking to increase my top end speed but I'm wondering if the gear set in the leg is an easier (or even possible) rather than trying to find a set of 30 degree props. I know the engine has enough power to support a change like this, but the drive is big question mark for me. It is currently sporting a 2.00:1 ratio in the leg now. Does anyone know if #1 the leg itself is even worth modifying, as I have been told that its already past what it can realisticly support for hp. #2 can I even change the drive ratio and how much work is it?

Any help or advice is greatly appriciated....

 

[haulnazz15]

Re: Bravo III drives

Wow, 450HP in an Arriva?! Aren't those at 20ft or less?

 

[Zackman]

Re: Bravo III drives

Does anyone know if #1 the leg itself is even worth modifying, as I have been told that its already past what it can realisticly support for hp.

Standard B3 is rated for 400 Hp. It depends on how you drive if the drive can take the additional horsepower.​

#2 can I even change the drive ratio and how much work is it?

Yes, but it needs to be done by someone with the right tools, knowledge and experience.​

What rpm are you at now at WOT? A prop change is probably your best bet. Also, the B3 is rated at 65 mph. You may be better off swaping the B3 for a B1.​

 

[HT32BSX115]

Re: Bravo III drives

I have recently purchased a modifed Arriva (by Bayliner) the boat now has a new marine 454 in it, and makes in excess of 450+ hp - currently there is a bravo 3 leg on with 26 degree props - I'm looking to increase my top end speed but I'm wondering if the gear set in the leg is an easier (or even possible) rather than trying to find a set of 30 degree props. I know the engine has enough power to support a change like this, but the drive is big question mark for me. It is currently sporting a 2.00:1 ratio in the leg now. Does anyone know if #1 the leg itself is even worth modifying, as I have been told that its already past what it can realisticly support for hp. #2 can I even change the drive ratio and how much work is it?

Any help or advice is greatly appriciated....

Howdy,


how fast do you want your boat to go now and what is your current WOT RPM?

If you're now spinning 5000 RPM at WOT you should be going about 57mph with the 26p props. (I get 57mph with 26p props 1.81:1 ratio & 4600 RPM)

If you could turn 5000 with a 1.81 drive, you would get about 63 mph (with your current 26p props), and if you could turn 5000 with 30p props, you'd run about 70.

With 30p props and your current 2.00 drive, (using this prop-slip calculator and 8% slip) you should get about 65mph at 5000 rpm.

Your mileage may vary.


I see 30p props on ebay all the time. from $500-700 in the Winter time. I paid $600 for a brand new set of 26p props a couple of Winters ago.


If you want to go fast, get a 1.81 drive. and put 30p props on it.


Cheers,


Rick

 

[96 Arriva]

Re: Bravo III drives

thanks for the incite folks - I really appriciate it

the boat for those who are curious is 24.5' ft

I wouldn't attempt to change the leg gears myself, was just wondering if its even possible, as I would love to run 1.81 or 1.6 ratio.

My speedo doesn't work right now but I'm seeing 5200 rpm on the tach at WOT - with the trim all the way down. As I trim it up I keep picking up speed/rpm. I figure I'm close to 60mph.

I'd like to boat to be able to run about 75mph without having to turn 6000rpm
I'm not worried about having enough hp just worried about how much my leg will take.

anyone have any idea what a performance bravo 1 is worth (preferably good used one) with a ratio of anything from 1.5 - 1.81

I'm just waying out options - as the budget detirmins the final decision.

 

[jaxnjil]

Re: Bravo III drives

http://www.mercurymarine.com/engines/inboards/sterndrives/bravoone.php

BI specs
Single, twin, triple applications over 100 mph for gas engines up to 600 hp

sound like a BI is the drive you need. it would be cheaper than any thing you could do to your b3.

as far as i know you can change the lower unit on the b3 to a b1 but you wouldn't have the gear ratio your looking for
it wouldnt be that big of a job to swap the whole leg. you could do that your self.

i'd be surprised if your 454 would live long at 6000 rpm for any lenght of time

 

[HT32BSX115]

Re: Bravo III drives

'd be surprised if your 454 would live long at 6000 rpm for any lenght of time

Well, it would do it if it were built properly.....

I don't think there is a 1.60:1 Bravo III

You can get it in 1.81:1, 2.00, 2.20 and I think 1.36 in the diesel Bravo IIIx

I suppose custom gears are available with enough money.

If you want all out speed and you're going to put a LOT of HP in front of a Bravo, you probably need to spring for a Mercury Racing drive.

More speed=more money!

Cheers,


Rick

 

[Mischief Managed]

Re: Bravo III drives

I'm pretty sure a Bravo 1 lower on a Bravo 3 drive with a 2:1 ratio equates to a Bravo 1 with a 1.5:1 ratio.

SEI makes a reasonably priced B1 lower. Put a 23" prop on it and you are in the same range as a set of 30" props on a B3.

 

[TilliamWe]

Re: Bravo III drives

Dave is exactly correct, a Bravo One lower install on a Bravo 3 upper that is a 2.0 gets you a 1.5:1 Bravo One. The price of SEI's brand new B1 lower is $895.

As mentioned above, no such thing as a 1.6 B3. 1.81, 2.0, 2.2 are the ones used behind gas engines. There is a 2.42 availble behind diesels. I am not familiar with the B3X and a 1.36 ratio.

Your boat is not going to run 75mph, no matter what you do with the outdrive. To increase 15mph will take A LOT MORE HORSEPOWER!

 

[45Auto]

Re: Bravo III drives

I'm with TilliamWe. If you're in the 60's with a 24' Arriva and 450 HP then you are probably at the point where power available equals power required and it's going to get real expensive to go faster. No amount of fiddling with gears or props will buy you more than a couple of MPH.

See this thread for explanation of "Power Required vs Power Available".

http://forums.iboats.com/showthread.php?t=225803&highlight=secrets