Sport Master Lower Unit

[cchandyman]

Greetings & Salutations to All You Bass Boaters Out There - It's Friday and I have a question about my Mercury OUtboard. When I bought my Champion boat it had a 1987 200HP Mercury XRi EFI outboard on it. Sometime in the past who ever owned it replaced the standard lower unit gear case with a Sport Master. I have not been able to find any information about this lower unit. What I need is a pictorial diagram of the unit so I can see what part numbers are required and the assembly sequence of the parts. Is there somewhere on the lower unit where it has a serial number or something?
Thanks for the help.