How much HP can "new" Bravo's
 

handle???

Looking at 600 HP, mucho torque........

Re: How much HP can "new" Bravo's
 

Scott.

There must be a 1001 threads on the Bravo One drive within the archives of OSO. Do a search on the Bravo drive as this question seems to get asked quite often. You will find a TON of info.

Re: How much HP can "new" Bravo's
 

There have been sveral threads on this subject, one more will not hurt.

RIce Hauler had 625 Zul's, never lost one.

I have (had) 600 hawks and twisted the prop shafts like candy canes after 125 hours.

I now have 700's being installed this week. As long as I do not do hole shots, slam the throttles like a dragster or try to to get air time like an airplane (keep them in the water) I do not anticipate any problems.

If you want to run like a maniacle race boat driver, install IMCO drives or 3's or higher.

Re: How much HP can "new" Bravo's
 

I saw some prior threads, but they were the old style Bravo's. And, agreed, the driver is the key, I have sen them hold up on 800+ HP blower motors, and get blown up behind stock 454 Mags...

I'm curious about the new "Volvocruiser" version. I have an opportunity to buy a B-1 complete, looking to put it behind 600 + HP and a bunch of torque.... Did not se a thread about them yet

Re: How much HP can "new" Bravo's
 

I had KE675s on a 37 A.T. Blew up a few, part of the reason I blame now was cause when put into nuetral, the engine rpms would spike up to 1300rpms. TMP fixed the KE's, you have to wait 10-15 sec. before they go back down and then engage forword or reverse. Very hard when docking. Im sold on anything with a tranny, No more bravos for me. Jeff

Re: How much HP can "new" Bravo's
 

J,

Yeah, that's another part of the equation for me.. Different ballpark maybe, same equation..
I currently have a TRS, thinking of either the Bravo or scrapping the Merctrans and going to a BAM or Velvet drive and keeping the TRS...

Re: How much HP can "new" Bravo's
 

I think the question here is the "BRAND NEW" style Bravo. 2005 version, not the old stand by... :D

Re: How much HP can "new" Bravo's
 

Not enough of them out there with real hours to make a judgement call. Has the upper/lower internals been changed, hopefully they are beefed up. Jeff

Re: How much HP can "new" Bravo's
 

Correct.. I'm told the limits are basically the same, the B-1 limits out @ 500HP, B-XR limits out around 625.
Guess I'll be sticking with the TRS for now...

Re: How much HP can "new" Bravo's
 

Just make sure you prop it on the back side of the TQ curve at WOT.

Re: How much HP can "new" Bravo's
 

Could you clarify?

Re: How much HP can "new" Bravo's
 

yea do that ...

Re: How much HP can "new" Bravo's
 

I think what they are saying, is that big props.are hard on the drives.

Re: How much HP can "new" Bravo's
 

skunkworks there scottyboy???? :evilb:

Re: How much HP can "new" Bravo's
 

You saw the boxes..




You knew I'd unwrap em..




Then what did ya think I was gonna do??? :drink: :eek: :D

Re: How much HP can "new" Bravo's
 

The TRS drive is a good old drive..can handle power and abuse...you can put the 600 on it with no problem. Back in the day they used to put more power than that on them racing and drive failure was never a issue..never!

Re: How much HP can "new" Bravo's
 

If you prop your WOT rpm too low or too close to your TQ peak of the motors it will tear up the drives that much easier.

Re: How much HP can "new" Bravo's
 

I knew someone was going to catch that, I should have guessed it would have been you :D The hard part was trying to dock, waiting for rpms to come down. :eek:

Re: How much HP can "new" Bravo's
 

If you like that, try docking a Donzi Blackhawk :eek: :eek:

Re: How much HP can "new" Bravo's
 

Higher pitched blades = flatter smack on the water when not sync'd with boat speed/rpm. Lower pitched=slice into the water easier no matter the mismatch. Add to that the more direct route of the power to the water on a high pitch as opposed to the "buffer" of more gear ratio from a small prop. Add to that the need to flog big props to get out of the hole. But hey,you can't beat the cruise speeds.

Re: How much HP can "new" Bravo's
 

Dude, wanna put down the pipe a moment and explain that?? :confused: :confused: :confused:

Re: How much HP can "new" Bravo's
 

I understand Scotts logic completely, on paper. How much difference it makes is debatable and is likley offset in one way or another, by size of gear teeth and other mechanical differences.

As far as his statement envision smacking a canoe paddle into the water horizontally, now try it with the paddle at a 90 degree angle to the water.

Re: How much HP can "new" Bravo's
 

Woops, Cooltoys logic...

Re: How much HP can "new" Bravo's
 

ive ran 750 hp on a 96 42 fountain four 4 years no down time yet,,, afrend runs 875 hp blower mots on a32 baha no down time,, 40 baha tripplehp 500 trashed --7--- drives in 14 months. ithink its the hole shot ore air time that does it. although i love to jump cruser wakes like a jetski. so how knows

Re: How much HP can "new" Bravo's
 

Scott, is this for the Critter?

Re: How much HP can "new" Bravo's
 

X boat :eek: :eek:

Re: How much HP can "new" Bravo's
 

honestly scott, i could just "detune" the 16 to make you feel better :evilb:

Root - die alpha die

Re: How much HP can "new" Bravo's
 

LOL, I'm already hearing rumours about your winter detuning project..

When do you want my SSM's for the dyno pulls BTW??

Re: How much HP can "new" Bravo's
 

Here is some info on old vs new Bravo 1's - http://go-fast.com/mercruiser_bravo_sterndrives.htm

As to the big prop vs little prop discussion above, it's all about the damage to the powertrain - powertrain being everything from the engine flywheel to the prop.

Here's the deal - powertrain damage is quantified as load^exponent times rate. In a mechianical transmission like a boat drive it's torque^exponent times rpm. The exponent used depends on the failure mode and can be either 3.33, 5.66 or 8. So, let compare a couple of way of putting 600hp through a drive. First is a warmed up 540ci belting out 600hp at 5000rpm which requires 630 ft-lbs of torque. Second is a high winding 502 producing the same 600hp but at 6000rpm would require 525 ft-lbs of torque.

OK, now let's use the lowest exponent, 3.33, and see the difference in damage between the two set-ups.

The 540 is 630^3.33*5000=1.05E13
The 502 is 525^3.00*6000=6.87E12

Therefore the lower rpm 540 would have +53% more powertrain damage than the higher rpm, lower torque 502! This change in damage relates 1:1 to the life of the drive.

Moral of the engineering story? If you want to keep you drive alive, keep the torque low and rpm up to get the power to the prop!!!

I almost forgot - this is ASSUMING the drive is sufficiently designed so the failure is in fatigue and not low cycle. Put 1000hp in front of an Alpha 1 and all bets are off!