Faint Blackish Scum Around Transom

[zippoo]

7.4L 454 Mec. 1997 529 HRS with through hull exhaust last weekend I was swimming around the back of the boat when I noticed a faint blackish scum on the transom under the ski deck I checked the oil level It looks good and oil is clean and not milky looking I also just changed my outdrive oil that morning. The only thing I have used different is I added Sta-Bill to the fuel could it be that the motor is running richer with the Sta-Bill added? The motor does sounds little quieter then in the past.

 

[Gary H NC]

Re: Faint Blackish Scum Around Transom

That is usually from a rich condition but if the Stabil caused it...doubtful...