I just found this site. There is a ton of info here.
http://www.boatfix.com/merc/mainmenu.pdf
Go to the Service Manual Link (below)
http://www.boatfix.com/merc/Servmanl/srvcovr.pdf
For Bravo 3 go to link "11" (below)
http://www.boatfix.com/merc/Servmanl/11/11covr5x.pdf
Scroll down to page "iii" and select the link for Gear Housing - Bravo 3 (below)
http://www.boatfix.com/merc/Servmanl/11/11d3r5x.pdf
I think you want 3D-8
There is also an installation procedure in that last link, and another in the Installation link at the begining. Good luck. Not sure if they know this link is open, so I suggest downloading all of the links before they close this link.