OK, so you really have a 68 Evinrude “fisherman” 6hp, correct?  Yachtwin is the 3hp model.

These are great engines, and it probably won’t take all that much to make a reliable daily runner out of it.

I would start with the basics, let’s drain the gear lube and have a look at it.  Remove the two large flat head screws and let the lube drain into a clean pan.  (DO NOT remove that phillips head screw of the shift linkage will fall apart).  The lube may be brown  in color, which is OK, just old.  Water contamination is indicated by “milky colored” lube.  Raw water spells big trouble, no lube at all is bad news as well.  Remove the propeller, check for fish line in the prop shaft seal.

Next, do a compression test on the engine.  These engines don’t have much compression, so readings between 70-80PSI are normal.  Extremely low or uneven compression spellls trouble.   Now check for spark.  No/weak spark on one or both cylinders means you will need to do ignition work, but you will need special tools to get that flywheel off/on.  Finally, there is the carburetor/fuel system to look at.

So, let us know how the gear lube looks and what the compression readings are, and well will go from there.  Don