Can someone give me an I/O history lesson?

I thought Bravo 1 was old, but just learned that XR was older and more apt to break (weaker shafts and bearings and such). Where is some good info?

Bravo 1,2,3,XR, XZ, racing, non-racing, etc.....

Thanks,
Dumb Ass Newbie

The bravo 1 is old it came out in the mid 1980's they made a few changes in 1990 or 91 to make them a little stronger and a little more sleek to pass through the water. The 1980's model was good until about 80mph before it blew the prop out without an aftermarket nose cone installed and the 1990's version was good until about 90mph. The xz and the XR outdrive came out about 2 or 3 years ago and are built on the same concept but with a few beefer parts to make them stronger.