What would cause the tower bearing to wear flat against the upr shaft?
Everything else looks great other than the bearing and shaft.

rpms and thrust, the bearings dont last forever in these, you have a high rpm super cat motor in your boat still and are turning a 5 blade maximus? I tear my drive down at least every 50 hours and always find some bearings that are not looking so great but by changing them before they get real bad the gears and shafts seem to last a reasonable amount of time, Smitty

Hey Bill,
Hope all is well.
The issue is the drive only has 15 hrs on it and I've been babying it for that reason. The lube was fine one day and the next its was burnt and expanded.
Usually as you I change every 20-40 hours as needed with real good luck for the power. We did build this last time with the taller tower bearing and I think it maybe a touch to tall.
Yesterday we rebuilt the upr with the standard tower bearing just to see if there is a diff.
It may have been a Chinese / Merc bearing. Who knows.