What's the deal? They came out in 02' and they're already discontinued. Are they that bad? I had a B1 in my 26 with stock 502 and never had a problem. So keep that in mind when you respond. I'm not racing or getting crazy, just want to know if I should avoid them. The reason I ask is I like a 35 500EFI that has XZ's on it.

An XZ is basically a X upper ( helical gears)
mated to a XR lower ( big propshaft)

I would see no reason to avoid them
with 500EFI's.

Yeah, I looked at the Merc link from another thread and saw what the differences were in the XR/XZ. XR All forged and XZ Near forged (the jist of the tech stuff). I was just wondering if the XZ line was a disaster because the line was discontinued after such a short tiime.

Running 598 700 Ponies Through Xz 1.36 No Probs 40 Hrs , Knock On Wood

Sleek,
Basically the XZ is an XR with Helical cut upper gears. They are the weak point in this drive. No weaker than a Bravo1. You do get a steel tower in the upper case and all the good XR lower stuff. The reason they discontinued them was because they had a lot of breakage with the upper gears. People thought they should be a strong as the XR and the upper gears would fail. If you put a set of XR upper (ribbed) caps on them they work well in LH rotation. Call it a B1 on steroids, but remember it is still a B1.
Some people perfer the Helical upper gears, and driven with the same respect that you drive your B1, there are no problems.

Hope this helps.
Dick

Had XZ and sportmaster lower case on my old boat (checkmate convincor) Boat had an HP500 ran 77.8 with the XZ. Sold the boat, the guy blew up the drive and replaced it with a stock XR could only get 73. Gears are stronger by the way they are cut in the xr but are slower. Do a search there is some info on this topic, I was involved in it a few years back. Good Luck, should have no problem with 500 EFI.