A while back Merc changed the XR gears to one's with a thicker floor. Apparently they used to have a lot of failures in that area. Does anyone know if these are the ones that are having all the issues?
I just upgraded to XR's last season, I picked up a set of used Merc reman units(not swept back), probabally 2005 vintage,with around 10hrs of use from the previous owner who bought them from Merc. Anyways, When Merc came out with the X,XZ,and XR drives around 2000, they all came with thicker floor gears which fixed the issue of blowing the clutch through the gears. These early XR gears lasted longer, and when they did wear out they would pit, letting you know its time to replace.
I'm not sure of the manufacturing timeline (maybe someone else does), but the later gears dont usually pit, but actually the teeth start to crack at the root and break off. I only know this because on my 2005 drives, upon an inspection(with 20hrs from me) I had a forward gear with a visable crack in one tooth. I was forced to keep using it, but am using that gear for reverse. I am going to have them apart for spring inspection soon and am curious what they look like now, I put around 60hrs on them so far against 750hp.
Bravo 101: As far as the X,XZ, and XR drives go, and someone correct me if I'm wrong. The X uses thick floor helical upper gears with a std 1" prop shaft. The XZ uses thick floor helical upper gears with the 1 1/4" XR prop shaft, and the XR uses thick floor straight cut upper gear with the 1 1/4" XR prop shaft.
LE