I read about the higher stress on Bravo top when setup to spin a l/h prop, but I can't understand what exactly the reason is, and how really critical that can be. Besides, does that apply also to XR drives with straight gear?

Map,
In a bravo drive there are two driven gears which are turned by the input pinion gear. Using a RH prop turns the lower gear for fwd and the upper gear for reverse. There is a cone type clutch that is wedged into the gear that is selected.
The amount of pressure applied to the driven gear is dependant on the amount of power put to the drive. With all the pressure to turn the gear there is some down force.
In a LH situation,, the pressure is applied to the top cap. It is a weak point. The standard top cap is very thin where the bolts hold it to the case.
With an older XR the case has a steel tower that the driven gear rotates around. The old style top cap has an aluminum tower and they shear off.
The new XR ribbed top cap has a steel tower in it and when studs are used, it makes the drive more stable and the top cap is much stronger..
I recommend fitting the XR ribbed top cap when doing any upgrades to the Bravos.

Hope this helps.
Dick

Aha! Many thanks Dick, now I understand. So, it has nothing to see with straight or helical gear...
My Bravo XR is a 2006 (swept back version, after OW240000), so it should have all the latest upgrades, as I understand?

the fancy cap looks like the one in this picture
( item 12/31)

http://www.mercruiserparts.com/Show_...nd+Drive+Gears

Thanks for the link.
It could be item 12, but it's not easy to tell because I never had to remove the Latham plate, and I don't know if there is any other version which is similar.
Maybe this pic is sufficient to confirm, for someone who knows the various types available better than myself? Thanks in advance!

You've got the "good" one Mr Gadgets was talking about.

Yes thats the fancy one

And thanks for posting that picture.

I just bought a set of those caps and am putting them
on my old style XR's ( with the old style cap)
and was wondering about some clearance issues
with the top plate, that pic. shows me what I'll need to do.

Thanks all for the reassurance! Makes me less concerned about my l/h prop setup.
Btw the boat is now perfectly balanced, so aside from the cost of a new prop I was fearing that she would have listed to port badly with a r/h prop...
@JaayTeee: I have some other pics of the drive, if they can be of any use, just ask. This is the one where the cap and plate can be seen better, though.

Do you have the same Latham steering he posted? I did and had a machine shop take 5/8 stainless rod and drill 3/8 holes through it....then cut it to proper length making solid spacers that bridge over the new finned caps. I then had to take stainless rod and make longer "bolts" so that these spacers could be used. I spent over $200 having all that made.....I have some extras and assuming I can find 2 complete sets are you interested in buying this stuff?

Not exactly the same...mine has the top
plate used with stellings boxes ( with the steering ram
attachment on the side) but the mounting points are the same.

Let me know what you have.