There are grooves on the clutch that almost look like threads and when the drive is engaged the cone clutch is supposed to lock into the housing (atleast that's the way I understand it when he showed it to me)

I had one drive that would have black oil after 25 hrs and the other was just the normal dark green, turned out to be a bearing going bad, replaced it and no problems since. The clutch was not the cause of my problem. 100+ hours since with no issues both drives same dark green at oil change time.

wouldnt just changing the lube once or twice a year be less of a heart ache and cheaper than trying to nail down the best lube? Not trying to be funny. On a stock bravo with a relatively stock engine, I dont think there would be much to worry about. My drives are fairly old, and the fluid comes out just as clean as it did going in. really probably could get away with doing every other year, but fluid is cheap insurnace.

OLD Drives = older Stronger gears

Yes changing the fluid is cheap insurance, plus you can study the magnets and catch a problem before it destroys the rest of the drive.

In a overpowered application changing drive fluid often, 20 hrs or so, is a must, plus running a better fluid like Bravo shop, Amsoil, Royal purple, etc. Still not magic though. Driving like a grandma helps a tiny bit, but again not magical like some misbelieve.

The only answer is LARGER GEARS, which wont fit in a bravo case. So Imco, B-Max, Arneson, X-Power, etc!

We put drive temp gauges on a boat once with XRs and 750 HP, and when one drive ran 20-30 degrees hotter than the other we would tear it down and find a bearing going bad. (and darker oil).

Its more than that... I have coolers and temp gauges. Cryoed gears and put together well. Never ran more than 175 degrees. Both within +/-3 degrees and then threw a tooth...

3 months ago I would have agreed, now, no. The cryoed gears are great but the metal they are forged out of SUCKS. Hence, loss of tooth (or teeth)

any idea what causes the bearings to go bad?

well obviosly Kieth, temp gauges wont tell you when a gear is going to break, but from a maintenance point of view if you notice your drives running that close on temp and all of a sudden 1 drive is getting warmer than the other, theres a good chance you can take it apart before you blow it apart. and repair it.
pstorti, alot of things can make bearings go bad, lack of oil, moisture in the case causing rust and lack of lubrication, metal particals going throught the bearings, from gear wear, shifting ring wear, inproper set up, loss of preload, heat etc etc etc

Anyone out there with Blackstone lube analysis on a Bravo XR drive? I am interested in iron wear PPM in particular (hours on lube and lube used also).