I would like to know what is recomemded for transmission fluid in a Yanmar 2gm 18 hp. Last fall topped it off and a few days ago when I started it up, I noticed that the engine bilge had fresh oil in it. (not the dirty stuff from the crank case) If I over filled it, is there some kind of breather hole that would discharge the excess? It didn't leak while the engine was running, but I never put it into gear. Any suggestions?