Re: 72' 18 HP Evinrude
Those holes are to drain water out of the lower unit. But they also can drain unburned fuel mix which would appear like a grayish or black gunk. Usually this happens when you are idling the motor a lot and it can happen if you have a too rich setting for your carburetor. You should verify it is not the oil from your lower unit. You can pull the drain plugs and inspect the condition of the lower unit oil. You might also be able to smell the gunk and determine that it is just unburned fuel.
