Changed out exhaust manifold earlier this year. No hour meter on boat but guessing about 20 hrs put on new manifold. Pulled drain plug on bottom of manifold a few days ago and lots of black carbon/soot came from drain hole. In fact, had to prod hole to get any water to come from drain hole. What is this black stuff? Manifold is new! Any input is appreciated. Thanks in advance.
1996 3.0L mercruiser
1996 3.0L mercruiser
