I have a Baja 302 that when shut off it leaves a nasty black film behind. It has 496's with 350 hrs each. I hate to pollute the h2o. Help me
First check the air intake and make sure the filter/flame arrestor is clean. Also, is your coolant coming up to temp? It should be between 160 and 180. Finally, a bad engine coolant temperature (ECT) sensor can cause this condition. Have a Merc tech put a scan tool on your engines.