I bought a used Evinrude boat motor. It appears to be a late 60's vintage in very good condition. The problem is I cannot find a serial number anywhere on the thing. The plate that should be visible when I have it mounted is gone and the little aluminum plug on top of the motor is also gone. It turns over but has no spark and the boat guy that is helping me is having a hard time matching up the parts we think are needing replaced. Any links to engine diagrams earlier than 1968?