It might help if you were to identify your boat make, year of manufacture, and your engines. Someone with the same boat/engine/transmission might come forward.
Here are a couple of links to Velvet drive schematics and you might find something there:
http://www.marinepartsexpress.com/BW...educ_Ratio.pdf
http://www.marinepartsexpress.com/PD...cr2service.pdf