Can somebody help explain why someone would want to run an xr over an x???

XR is stronger and beefier.

X - has XZ upper gears (spiral cut) with Bravo 1 lower and the smaller 1" prop shaft

XR - has XR upper gears (straight cut) with XR lower and the 1.25" prop shaft.

XZ - is basically an X with a XR lower

I'm sure the experts will chime in with more specific differences.

xr is good for 600 hp
x is rated for 450 hp

Does anyone know what bravo came from the factory on a 1999 HP 500? I found some old specs on the HP 500 Bulldog that refenced drive options for "bravo-1" or "bravo-1 performance". Never heard of this before, was there some intermediary upgrade before the XR and XZ's came out? I know they had a good run, but it's hard to believe that Merc didn't do anything to the B1 in 10 years and just bolted them on their racing series motor rated at 470 prop hp.

Bravo 1 Performance from that era had shot peened gears. Suppose to solve the worlds problems, but did not really improve anything. They used it on the Diesel motors also.

Dick

Thanks - if mine blow up - which I assume they're overdue for being paired to hp500's and 10 years old - what would you replace them with without going nuts on the price? Mine are mounted on stellings extension boxes. I'm told by the previous owner these were original from the factory.

Joe,
if you dont have enough power to knock the teeth off the helical cut gears I would go with them.. The Bravo 1 X is a good drive and should hold up, driven with respect.
The XR upper gears have been snapping teeth off right at the root. We didnt see that 4 or so years back. So something has changed. I hate to build an XR these days.
Hope that helps.
If your cases are in decent shape, they can be upgraded.. with steel towers, X gears and good top cap.

Dick

If they lasted 10 year and did not come apart I would replace them with the exact same thing . Just my .02

If you read Powerboat the original B1 is now considered junk and the only way to go is XR, IMCO or Teague drives (no conflict of interest there!) or NXT God forbid that price tag. Powerboat has become the Teague Fountain magazine and I am considering ending my 2 decade subscription run, but I digress.

On a lighter note, I have a friend with a 1989 22' Checkmate 454/365 mag with Bravo 1 and we beat the heck out of it for years upstate NY. The drive was probably pulled off 3 times in it's life and never needed any significant repair until the day we "found" a submerged rock in the lake One could argue that it was subjected to less stress since it was bolted up to a light boat, but an admirable performance none the less.

Mr. Gadgets knows his stuff. Went through my Bravo I's three years ago, with no problems. I'm pushing quite a bit of hp, but NA.