Based on your serial #, you have a motor from somewhere in the early '80s (for example, my 30EL689407533 is an '82). There are a few threads on here (you'll have to search) that give a link to a reference table to determine the exact year.
Based on my experience, with a 1980's Mariner, your parts searches will be much easier with both the serial # and the year. A lot of the factory parts will show "NLA" and you'll have to go to a third party source. The third party sites may provide listings by serial # or by year/model, but usually not both - again, just my recent experience.
