XR3's break too. Here is one off a 370ss with 525's

My friend owns a 2003 47 excalibur with 496 whipple motors,,, they make about 700hp and 800lbs of trq. the boat weighs in at 22000 fully loaded... he gets about 100-125 hrs a drive,,,, the boat came with bravo 3x drives... he had to rebuild them to handle all the power and weight of the boat(59mph on gps) you need to put the XR upper gears in the top of the drives,, also need to take out the needle bearings that come installed in the XR gears and replace them with a larger bearing. This will take the rock out of the upper gears.. also have a full tower installed by Max Machine Worx to support the lower part of the gears..Install a larger top cap, install a drive shower and finally use Amsoil severe duty gear oil 75/90 wt and mix it 4 to 1 with lucas engine oil treatment... this oil combination will double the life of the gear and stop the pitting of the teeth. there isnt much that can be done with the lower gear set. they will last you as long as they are properly shimed to have the correct backlash,, we lean alittle towards the tighter side.. there are only two shops that i trust to set you up right ,, Coughlan Machine in Norwood MA or Max Machine Worx in Lake Havasu,, others may have there""guy"" but ive seen these drives hold together over the years,,,,

Arneson Bravo Conversion kits.......Hmmm

I discussed the options with the Wisconsin Formula dealer, and they are willing to do whatever I want. While we hear about these drives breaking on this forum, there are likely many that are fine for a long time (we just don't hear from those guys). Who knows the ratio for sure. The Imco performance drive was the best possibility I saw as reasonable alternative, but the cost would be steep. So I'll give the Bravo 3 X another go. I'll let you know if it blows. If you don't hear from me, things are fine...

FYI: 300 hours now and no more issues. Original drive fine and that replaced drive have been fine. Replaced gimball bearings last fall when drives were off. One was rusty due to small slit in bellows (muskrat?) and other replaced just because they were working on the other one anyway and parts were reasonably priced. A few best practices that I keep in mind with this heavy boat:

Do not can the throttles, bring up on plane gradually
Never launch the boat in large waves
Always pause in neutral when shifting between forward and reverse
Remove drives annually for maintenance

I do not drive her like a go fast, so these things are easy to follow.

do you still have that boat