You are right, it's a 1980 3.5
You should be able get most power head parts from a small engine shop. Here is another place to get them, it's also a very informative sie: http://www.discount-marine-parts.com/
The numbers on the little tag near the carb are the power head id numbers. Give these numbers when getting parts for the power head. The 14139A is the chassis number. Give this number when getting parts for the lower unit.
Eskas are simple little motors, but are prone to carb problems, so make sure the gas tank and carb are very clean. Have fun!
