I have a 1984 25 hp evinrude. When i pulled lower unit to change impeller i noticed soot (carbon) buildup all over inside of casing water tubes ect. Is this normal my only other experience has been with a 1974 25 hp johnson and it was clean. What would cause this and what should i do (Clean it out) Allso i have only run motor in a barrel of water it smoked alot and water looked like a oil spill
