RollWithIt

A member at my marina has recently put a built 454 motor in his boat that came from the factory with a Bravo 3 Drive. He loves having the dual props. But, he's being limited on the top end by the factory props. So, he's considering swapping out the Bravo 3 for a Bravo 1 drive. How difficult is this and what would it entail? Is Will the Bravo 1 bolt up to the existing Gimbal? Will it take some custom adjustments to make it work? Looking for advice from the outdrive Gurus. Thanks for any answers.

Pismo10

Bolt it right on.

RollWithIt

Ok. Easy enough. LOL. Whats happening is the guy put in a built 454 which was dyno rated at 460 hp. He is maxing out the rpms at 4800 turning the two 26 pitch props on the Bravo 3. Top speed via gps is 48 to 50 mph. He is planning on changing out the rev limiter. Supposedly the new engine is good to 6000 rpm's. So the hope is that with a Bravo 1 and some prop testing along with the rev limiter changes that he will be in the 70+mph range.

GOODT

1) switching from a # 3 drive to a #1 will cost him speed the # 3 much more efficient if worried about it holding up go to a bravo 3 x drive

RollWithIt

The big problem he is running into with the Bravo 3 drive is that there are not many choices for higher performance props. At least that he's found. He is running the 26 pitch. But I guess one of the two props has a different hub and there just are not too many performance choices out there other than the factory props.

Would it make sense for him to simply try to change the rev limiter on the setup then? Or can he change the drive ratio by simply switching out internals? Currently has 2 to 1 drive.

SeaRay Jim

I find it hard to believe he's just going to up the rev limiter and take a 454 that's turning 4800 RPM and start turning 6000 RPM. I doubt the motor is built to turn 6000 RPM and certianly isn't cammed to turn 6000 RPM if he's turning 4800 with 26p props. Of course I have not idea what the boat is but that sound about right.

Oh, the BIII props just slip on the prop shaft; no hubs like BI. Fore is larger and aft is smaller, but they just slide on (you need to you align/time them right).

BIII props are BIII props. There is nothing else unless he goes to the new BIII XR props. However, he's not near a speed range where he's out of efficiency with a BIII. The BIII props can be worked to get what he needs. At 4800 RPM turning 26's, he really can't go any bigger so if he indeed needs to turn the motor up (need to know what the peak HP range is for the motor) then dropping to a 24p will get him up to 5100-5200 RPM or work the props to get more. There are choices.

But if he really want a BI for whatever reason, (and he's not going to magicly get a bunch of speed from the swap) swap lowers and go as long as the gearing is right. If his BIII is a 2:1 then a BI will be a 1.5.

Sugest to him to call Brett at BBlades. I know someone that just had BIII props done and so far, they are awesome. These were a special case like mine, where we're cavitation burning (and cracking mine) but Brett seems to have come close, if not resolved the issue for this guy as well as improved performance.

BTW, I'm running about 575 HP (540 CI) through mine with no problems, but I'm intentially easy on the drive. I know someone that ran about 625 HP (Whippled 502) and after upgrading the upper gearset, had no problems.

Pin the throttle with a Whippled 502 in front of a stock BIII and you eventually break things in the drive.

JUKED YOU

i disagree, i could be wrong but i was always under the impression the bravo 3 was a drive designed for larger heavier boats that need added thrust in the lower rpm range....the bravo 3 creates more drag with the 2nd prop thus causing lower speeds....the same way a single 3 blade prop will be faster than a single 4 or 5 blade. The bravo 3 sorta hits a wall at about 60 mph ...of course given the fact that each prop is dialed in to run the correct rpm range I would think he would gain speed, but we also need to know what size boat this is and how much it weighs to accuratly determine if the switch would be a good choice.....am i wrong?

RollWithIt

The boat is a 23 foot crownline. I dont know the actual weight of the boat but it is probably between 3 to 4 thousand pounds. According to the owner of the boat, there is a Dyno sheet for the motor. Ive never seen the sheet but he says that the power does not drop off till the upper 5K range in RPMs. It does seem odd that the motor is supposed to turn up to 6k rpms. But that is what the builder says it will do. I did go for a ride in the boat and can see the tach bouncing at the 4800 mark as it hits the rev limiter. I wonder if it could be possible that there is that much added drag to the motor by hooking it up to the drive and running in the water compared to a dyno that he is loosing the rpms there.

correct me if Im wrong. But my understanding of the process is that when you step up in power, you can now turn the existing prop at a higher rpm because of the stronger power against the same resistance. Therefor you have to step up in pitch so that you dont over spin the motor. Thus, giving you more top end speed by being able to run a higher pitch prop.

boatman22

I just changed out engines in my .38 Special. I was running 454 mag’s with BIII’s and max rpm’s was 5000 with 26P props and 61 MPH GPS top speed. I now have a pair of 577ci Dynoed 650HP with B1’s and the first time out this past weekend was 70mph at 5100RPM’s Max RPM’s with 28PBravo props, should be 5800. The big difference I see between the drives is around the dock. and getting on plane. I miss my BIII’s ,I might put them back on to just try them and see what happens. It is an easy swap between the 2 drives.

Wobble

I have yet to hear of any Bravo-3 combination that will top 62mph. I have always assumed that drag was the limiting factor.

I would agree that they are awesome up to that speed though.