I posted before when I broke my vertical shaft in the upper unit. My drive is a 2004. When I broke the shaft, I wiped out the tower that holds the race for teh drive gear. I had another case, older from what I can tell, but its a bravo upper with the proper oil passage, but it was a different gear ratio. The other case is in perfect condition internally I installed new needle bearings, and race on the tower and top cap. When I went to install my drive gear assy, it binds hard with the pinion gear. From what I can see, the lower gear is too high. I measured to the top of the tower on both cases and there is a pretty big difference in height. No matter what I did, I couldn't get the lower gear to mesh properly. I thought all bravo uppers were the same? The gears that came out have a much sharper taper than mine. My drive was a 1.81, the one I'm swapping over was a 2.0. Anyone have any thoughts?

You may going from low floor gears to newer thick gear. Thick one uses thinner shim. If you have old style case with shim size stamped in case. ie 94. New style will use .064. Don't hold me to the .064. Could be .054. So look it up. I am not where I can look for now. If you have OW xxxxxxx case it's needs to be Shimmed with tool.
Also check tower bearing hight. Some cases it sits lower

Yes - replacement case is 94 shims, damaged case is 64 shims. But I put the lower gear on the tower with no sims and I couldn't get it to mesh properly. Bound with he pinion nut finger tight. Can the tower be different? I measured both gears - they look the same. Do you know what dimension would be different, thicker vs thinner floor?

here's the bulletin for installing the thick floor gears in a older case.

https://www.mercruiserparts.com/bull...2001/EN_17.PDF

page 5 makes mention of positioning of the inner race

Thanks! Huge Help. Should be GTG now!

When you install the new Thick Floor Gears into an old style Thin Floor Gear case ,,you must drive the tower race & and top cap race down .125 past flush with the surface , as shown in the photo in the Mercruiser Bulletin

hopefully you get this lol what did you end up doing? I’m in the same position.