How about a quick lesson in B1, XZ and XR?
 

Can anyone supply a succinct technical description of the merits of each of these drives by upper and lower?

Looking for relative strength of each by upper and lower and common failure or weak points on each. I have some knowledge of this but only from what I have heard or read here and there.

Tim T.

See if this helps:
http://go-fast.com/mercruiser_bravo_sterndrives.htm

Prop shaft on XZ?
 

Tim,

You said on the phone that you bought an XZ. Are you going to have to switch props because of the larger prop shaft, or is the hub on the prop removable?

Lesson one, everything cost more. I have the insert style hub kit on my 27. New insert is about a tank of gas. If you are wanting to try the no-cone lower your hub will fit. If you want to try the 1.5's we got to swap lower from the old B-1 to the OM lower. Better get some gear oil, we are going to need it!

Just an addition: The Bravo 1 is now the Bravo X which was changed late in the 2001 model year. It supposedly added beefed up components in the upper that are nearer to the XZ and XR who's components are beefed up in the shaft, lowers, and auxilary bearing areas too. That's what Merc says...

Having had an XR apart I can reaafirm that the drive is significantly upgraded over a Bravo 1. The billet tower, stronger shafts, and better gears. XR has straight cut gears, XZ doesn't. XZ has better and stronger gears over B1. XR and XZ have the billet tower and I believe the Bravo X has as well. The bravo X has the same upper gears as the B1, with upgraded billet tower.

Tim,

Can you recall if Mike's 23 M+ has the newer-style removeable insert? If it does, I could just toss the 1.5 on there to compare.

I think so, but then again what day is today?