I haven't been able to find anything past 1998 for the year references, at least for those motors.
The best I've found are parts lists and they start with serial numbers 0G and up. 0T and 1B should be a continuing series of the same thing but I have no reference proof.
If you do find a year reference for them, post the site.
Here is what most sites have.
http://www.warnersdock.com/Modelyearlookup.htm
http://www.obparts.com/years/mercury.html