How much H.P. can a Bravo III take?
 

I have a heavy Cruiser (9000#s) with a converted 7.4MPI. Mag inners, Merlin heads, Gill exhaust and a 5PSI Procharger (just about ready to run her). The factory says a stock Mag will develop 560HP with the 5PSI pulley. The boat , last year, did 46MPH with the stock 7.4MPI 26" cupped props (4600RPM) and a stern jack. I have a drive shower on what I believe to be a higher geared otherwise stock 1998 Bravo III. Anybody have experience with high HP on a stock Bravo III. I know their are other upper gear-sets with bigger universal joints but I do not know if these are compatible with my stern jack.

Re: How much H.P. can a Bravo III take?
 

im not a pro like most of the guys on this site. There are people on here that know anything and everything......But i can give you my opinion....The amount of weight you are pushing is going to destroy that drive with the hoarse power you have, i dont even think if you ease it on plane it is going to last on top end at wot......evrybody is in search of that faster top end so i imagine you are too. But you never know i would have another boat following me with a strong rope aboard............

Re: How much H.P. can a Bravo III take?
 

Ive never seen it hooked up to more the 425 hp, if going higher then that go with the new bravo 3 X drive

Re: How much H.P. can a Bravo III take?
 

Is this a 9000 lb boat with a single? I would wonder if any Bravo is going to handle much power in that setup.

Re: How much H.P. can a Bravo III take?
 

had a customer last year with a doral that was about that heavy with twin bravo III went through 3 drives onthe third we got merc to upgrade him to bravo 3 x drives didnt have any more problems

Re: How much H.P. can a Bravo III take?
 

Assuming single engine:
If you are running the 7.4MPI otherwise stock internally with the procharger, then I think you have two potential grenade items....

I would expect an exhaust valve to end your engines life soon, unless you had the computer correctly reprogrammed, which is really hard to do, and checked the volume capability of your fuel system very carefully....

My guess: An exhaust valve will come apart, hit the piston, tearing it into a million pieces, allowing the rod to crater the block, and then you will have a few hundred pounds of pure junk sitting in your bilge...

I have seen that happen twice...

Then there is the drive, with 500+hp and a 9k lb boat...You already know to take it easy out of the hole...

The first time you have a few brews or try to pull up a skier with a hole shot, you will hear a 'Kaboom' with no traction after that.
===
Good luck!
Kent

Re: How much H.P. can a Bravo III take?
 

The boat , last year, did 46MPH with the stock 7.4MPI 26" cupped props (4600RPM)

Is it me, or does that not sound right? I would think you would be going a lot faster then 46mph. I would think more like 65mph. Im even surprised a stock 7.4 could turn a 26 pitch prop.
I can barley turn a 25' w/ my 502

Re: How much H.P. can a Bravo III take?
 

Bravo IIIs have a different ratio... :rolleyes:

Bob has been running with a supercharger for some time with good results.


Hey Bob,
Sounds like you put a nice package together... :D
Either rebuild your drive with XR components or buy a new B3 XR drive. There is a kit to convert your existing gimble to run the HP drive if you go with a new XR.
I would also ditch the stern jack, those things add lots of stress... :eek:

Re: How much H.P. can a Bravo III take?
 

My father just purchase a boat with a 496 and a Bravo III XR drive. Merc says the XR drive can handle up to 525 HP. You might be pushing it on a stock III with that HP

Re: How much H.P. can a Bravo III take?
 

Last season I hooked up a old (ap.-95) Bravo III (1:1,68) to my new single 496HO. Boat weigh ap. 4000 lb and ran 70 mph. @ 4900rpm. Had no problem at all!

Re: How much H.P. can a Bravo III take?
 

I don't even want to start talking about drive "booming"!!!! :o

Mine's close to 6000# on the water, roughly 575HP 540ci. Stock was a 7.4 MPI with BIII 2:1 gears and a 26p. I'm now turning a 30p prop.

First, 9000# and running 46 MPH with a 26p, I'm assuming it's a 2.2:1. I have a hard time seeing a 7.4 MPI push 9k that fast. Mine stock would kiss 50 MPH and slightly modified hit a best of about 53 at about 4500-4600 RPM.

1st season with the new motor, the best was about 65 MPH and turning up in the 5200 RPM range and burned up the rear prop. Cavitation burned really bad to the point that it developed a stress crack last day out last season.

The props are fixed and labbed and I'm hoping to get her out this weekend for 1st splash. I'm also on a constant hunt for spare 30P props. :D

I know I'm pushing the drive, but I don't hammer it out of the hole and it's carb'd so I don't have the same issue you might with straight arming one with a SC. So far the drive seems to be doing fine and I hope it stays that way.

Re: How much H.P. can a Bravo III take?
 

SeaRay Jim, which X-dimension are You running?

Re: How much H.P. can a Bravo III take?
 

I don't have a clue what the x-dim is on mine. LOL It's a Searay Sundeck (deck style boat). Whether a different x-dim would help or not I don't know. It's not the kind of boat you'd normally go to that much trouble with to get better performance. Actually, it's not the kind of boat you'd put a 540 in either, but no one told me that until it was too late. :evilb:

Seriously, there'd be way to much to do to try to get performance out of a boat that's not designed for performance, so tweaking things like x-dim would be saved for a boat that would be more fitting for it. If I started doing that kind of thing, I'd likely loose some of the other things thatare so great about this boat like normal handling, putting around etc. Kind of like putting a SC big incher in a Dodge Caravan then tweaking aero-dynamics, weight etc. and still expect to load up a bunch of 8 year old soccer players and going to Chuckee Cheese in comfort. :D I've got a great balance right now as long as I can keep things from breaking! ;)

Re: How much H.P. can a Bravo III take?
 

I have a spare set of 30's. Too much for my 500HP 502.

Re: How much H.P. can a Bravo III take?
 

I've found another set I'm trying to get and already have 1 spare set but the rear prop has a crack I'm not going to have messed with so I'm considering it a paper weight. If I can find just the rear prop that would be good, but if you'd want to part with your set and if they are solid with no damage to the blades, splines etc. what would you want for them? They'd be going to someone to be labbed etc. so I just need them to be solid and sound.

Are they standard or cupped?

PM if you'd rather.

Re: How much H.P. can a Bravo III take?
 

Jim I sent you an email but am having some problems with Email.
Did you get it?

Re: How much H.P. can a Bravo III take?
 

Got it and replied! Thanks