Need help IDing motor

I was given an Evinrude or Johnson (???) outboard. There is no data plate with model # or serial #. I'm not even going to think why someone removed it!!! My son talked with a guy he knows by phone and without being able to see the motor, his best guess is around a 1979 85-115 hp. The number on the welsh plug is J 3860786. I've looked on other sites but I can not find a listing of just serial #. I'd like to find out what year it was manufactured and the hp of the engine in case I have to chase down parts. Are there any other numbers that would be specific to a particular year and hp than I could look for?
Thanks for the help.

There aren't any Serial number listings for Johnson/Evinrude motors from that vintage that I know of. Those motors were identified by model number. Usually the nameplate with the model number would be on the mounting bracket on the port side.

You can see what the the model numbers should look like here:
http://www.marineengine.com/parts/john_model_guide_pre80.html#j115hp

You could also try posting some photos of the motor here and someone might be able to help identify it from them.