Well, after looking at your pic I'd say the mesh pattern in mine looks about like yours so maybe it isn't "that" deep..

Pretty unfortunate. Not available this week but I'm gonna start looking hard for the gears in other places.

Not holding my breath.

My hope is two fold:

1. That they can be found without Merc.

2. If they can, then hope that maybe Merc "told" the manufacturer to make them "cheaper" like the 525 cmi's and that perhaps a set off the shelf might just be better treated etc..

It is my thought that these low hr failures are due primarily to improper gear break-in. Mating surfaces of teeth are rough when new. High pressures on rough gear teeth during initial runn-in will cause loss of lube film and then galling of the teeth. A properly worn-in gear set will have smooth tooth contact areas and better lube film strength. This is prevelant in miter gears (XR) more so than spiral bevel gears (std bravo) because the tooth contact area is smaller on miter gears. Spiral gears have more of a sliding action and less "point loading".

BT

No wot for first 10 hours - vary speeds and throttle during that time. Then make some short passes wot in a few second bursts and change the oil often using one of the most expensive gear oils you can find....

What else can you do?

When you see a gear set flake out like that it has nothing to do with break-in. It's a simple fact that they are lacking the proper, time consuming and expensive heat treating.

You can rest assured Merc has them made as cheap as possible (kinda like those 525 cmi's that keep cracking often).

When you buy a brand new drive and pay the coin, going out and running the snot out of it is not the first thing on my agenda...

My thought is that it is probably not practical to break these gears in properly in this application. You'd need to run them at 1/2 load for several hours. Even getting on plane would ruin that process. They need to be "pre broke in" by micro polishing the gear faces or some other method. All in all I think the spiral cut gears are superior in application due primarily to what I mention. Maybe John the drive man will let us in on how he breaks in new gears.

If too much load during “Break-In” is a large part in shortening an XR gear sets life; it seems like going down 4” or more in prop pitch would help. Has anyone tired that?

That's a good idea. I was also thinking idling at a fast no wake speed for a couple hrs might do it. For the price of wrecked gears it may be worth it.

The lower gears in all Bravo's are straight cut
gears ( just like what XR uppers are) and they
dont require babysitting.

Lower gear failures are much more rare than uppers.

The B1 on my boat has XR upper gears in it.. Installed in 2001 or so.. I never really took extra care in breaking it in. I did the normal easy on plane, no WOT for a several hours. Since then I change my oil religiously every 40-50hrs, run it hard when I am on Lake Michigan. With my boat I cant really tell when the prop leaves the water. Had a fellow boater ask why I never let off when air born.. Told him I couldn't feel it. So I dont pamper it. The drive has 330hrs on it. I had to change out the upper pinion gear at 40hrs because it was soft and going away. I put a new one in and never changed the setup. Took it easy for a while, then back at it. No metal shavings on the magnets, last time I drained it.
But one thing that I am sure of, the lash variation on the XR gears and even the lower gears is all over the place. It used to be .002-.003".. Now it can be up to .010". Put a gear on an index table that shows if the teeth are all in the right place, tell me what you find.
When I started seen the lash change drastically, soon after the teeth started snapping off the upper driven gears. Used to be 250hrs was normal for 750hp in a light 6k lb boat. Now the pitting starts early on..
I think Merc needs to go back to their first supplier and hopefully all the old duffers that knew how to make them are still around.
Sorry about the rant, but just had to vent. If we could turn the clock back 5yrs, I would purchase a couple thousand sets of them.. and bring them back to the future.. Problem solved. :)

It's a complete f cking from Merc. They know these gears are junk. It's all about making money. Just as someone said about the headers. Suppliers can make gears hold up to tons of torque in diesel applications for industrial equipment.
But they can't make a gear hold up to 500HP in an outdrive?

Lower gears are in a different location in the drive train. Many additional variables would come in to play when comparing thier wear to upper gear wear; noise, shock loading, lub bath, heat and so on. My comment was concerning wear of different gear styles in the same position in a drive train. It is a fact that miter gears take much more babying on breakin than spiral cut gears, no matter what tpye of gearbox is being discussed. The lube film is key to preventing wear.