Superchargers and outdrives
 

Roots Screw or Centrifugal. Which one do you think is the hardest on outdrives.

It's all in how you work the throttles. My experience with NA and making a drive last is down to pretty much 3 things within reason. 1, lower rpm going in and out of gear the easier it is on the cone clutches. 2, is getting on plane with ease without loading the engines with torque. Don't treat like a 1/4 mile drag car. 3, your re entry. Timing with getting back into the pins can be good or bad day. Just being sensible is crucial. What kind of drives/trannies. Boat length weight etc can all come into play. Sorry I didn't directly answer your question but just threw out some basics that you likely already knew but...

That same applied to twin roots also.

They're all hard on drives. Best advice I can give is to build the engine to turn 5500+ rpms with a blower or turbo.

If that's so then I'm screwed. I'm propping for about 6,200 however won't be miles on end 8-71/548. Just here and there and to pass the locals. Yes you to E32, lol...

I've toasted a few drives however was from abuse. I don't know maybe rpm could have been a contributing factor. Who knows.

I would vote a roots supercharger is harder on the drive all other variables being equal. My opinion is based on immediate boost at all rpms where a centrifugal supercharger has to spool up. I understand centrifugal is a more efficient supercharger but if you want results without waiting roots will instantly assault your drive train. Ask me how I know! This performance sure does get expensive:grinser010:

Yes it does get expensive. No matter what the builds it's extremely difficult not to stab the throttles at that perfect rpm for a rush. Getting from a to b now is much more thrilling than later. I do see you logic second wind.

Ha- you won't be passing me, not with 2400 hp and twin quads.

I have centrifugal superchargers and when I was breaking my bravos all my drive problems happened above 3,000 rpm and I was not jumping any waves

Very interesting reading

I am planning on around the 6 grand mark also. 540 going in a Activator 27. Was planning on procharging but dont want to do the blow through carb thing so decided to go roots carbed.

Not really, max torque is between 3-4000 rpms.

maybe with you cams. Hah

what kind of power

800 hp

I'm guessing my Procharged engine will unfortunately be JUST as hard on drives... :evilb: :)


https://c1.staticflickr.com/5/4666/2...a2fbe512_b.jpg

I've been running 700 HP through a pair of bravos for about 500 hrs. The drives are original circa 1992. Over 1100 total hours on the drives, never opened up. I'm easy on and easy off and it I air it out it's not intentional. Don't get me wrong, I use every bit of power I have and I beat on it when someone makes me do so. It's all up to how you work the throttles.

Yeah I guess add 5-600 on to each of those numbers.

Boat size and weight has a lot to do with it. I ran 650 hp through bravo X drives, in my 29 Formula. Never really an issue. Put that same combo in a 38 and it’s going to be a lot harder on the drives. That’s why I sold all my bravo stuff when I bought the new boat, and switched to SSMs. That’s when I was planning on sticking with my old engines. No way those drives would last a day with the new power.

I did build a drve for a guy guy with a 25 Baja, 950 hp. It too had X gears In an IMCO case. It made it through his Poker Run, and that’s all he cared about. I was honestly shocked it stayed together. That’s a lot of power for a Bravo.

Centrifugal chargers seem like they’d be easier on the drive because they make power higher up in the revs when the boat is up and loose, but they make so much power that they require huge props that struggle to get out of the hole loading the drive even more. I’ve heard stories of drives living forever in rough water but blowing them up in smooth water with the constant relentless tension.

Moral of of the story: you’ll have to pay to play once X amount of HP has been exceeded no matter how you achieved it.

Come on granny........:D.........and second Im shocked 800hp is breaking a bravo....:party-smiley-004:

That "granny" talk will end when I get to TR!!!!

Nothing looks better than a carbed roots blower motor IMHO. Well maybe a giant PSI carbed blower motor but that’s it. Good choice sir!

When I had my blower boat I was always easy on the sticks getting on plane. This is a lot of load on your drives and where you are most likely to break them. I never had any issues but I also had Teague Platinum XRs as well.

Plus the concept of being good on the throttles, can vary. It' easy to work the throttles when you're jumping over a random wake from a cruiser that you encounter a couple times a day while boating. Not so much when you're on the ocean or great lakes, and your on/off the throttles every 4 seconds for 30 plus miles at a crack. High x dimensions and rough water is the number 1 drive killer in my opinion.

If you are going to run big power, and currently have bravo's, saye your money to convert them to IMCO SCX uppers. To save some money, you can run an IMCO SC lower. Here is the deal with Bravo's.

There is a lot of smoke and mirror sales guys out there. Special shafts, coated gears, better bearings, it goes on and on. NONE of it, is going to do much if anything, OTHER than drain your wallet. The clutch shaft is a major weak spot in the bravo drive, and there is nothing you're going to do to improve that. Steel towers will help keep everything lined up, BUT it won't fix the issues. Mr. Gadgets in my opinion, has the best tower upgrade for the money, so be wise when spending your money, but it has its limits as to what it will do.

What I would suggest is keep your eye open for a nice set of IMCO SCX drives. They pop up from time to time, and they will handle the power you will be making. I've seen them as low as $7k ea, which isn't a whole lot more than a rebuilt bravo XR. Speaking of XR's, 200 hours on an XR, and its most likely due for new gears, at $1600 plus labor. Again, if you're planning on new power, start saving for new drives, and don't waste a penny on making your bravos "better".

I agree on the scx. Except I think I would opt for the scx lower as well. My buddy Joe had scx uppers, with sc lowers, on his 42 fountain with a pair of 1000s. He sold the boat with very low hours, like maybe 10-20 hours on the new engines. I think the sc lowers were as fresh as well, and they new owner took the lowers apart and they were shot. Both lower gear sets that is.

I think the reason the #3,4,5,6,8 drives handled power well, was because they had two gearsets in the lower. Each driven by it's own vertical shaft. Putting all that torque thru one gearset that has to be small enough to fit inside the bullet, is just not strong enough for today's engine. This is also why the power handling capability of a speedmaster drive, can be immensely reduced if set up by someone who isn' familiar with them. If each lower gearset assembly isn't setup so that power gets split equally to both sides, they will fail prematurely.

Great point about high x-dimension and rough water. Throw high horsepower mills into that equation and parts start to break.

I agree, but to keep cost down, the SC lower will work. The SCX lower is stronger, but for that bigger gear set, the lower is bigger, and I've had guys tell me they lost 8 mph with the SCX lower. It's all a trade off, personally, I'd take the speed loss, for added durability. I know IMCO has a new lower that addressed the speed loss issue, but I doubt you would find one used.

I'm trying to decide if I'm going to run drive guardians. I would think with a high X, it would be a wise move.

We just had a DriveGuardian installed last Fall. Time will tell if it makes a difference. Without the DriveGuardian the SCX upper/SC lower lasted 1.5 seasons before we fractured the lower case. High x-dimension, 850HP, I like to drink beer.

Bud Friday!!!! :ernaehrung004:

I try also now the Driveguardian on supercharged engine! Afterr reading a lot about it,i think i will help to last a Bravo much to live longer on high HP!
Michael