1. A healthy sparkplug in a healthy marine engine, comes out of the engine looking pretty much like this: the insulator nose and electrode should be a deep brown color, with no abnormal deposits.
2. If you see water droplets, they may mean a leaky head gasket or exhaust manifold.
3. If you see aluminum speckles it may mean pre-ignition and impending “meltdown”.
4. If you notice a whitish electrode and/or insulator nose (as compared to the normal brown color) it may mean a very lean fuel-air mixture
Signs 1 through 4 point to a very unhealthy engine. See your dealer!
Extra Point: If one or more plugs are not “colored in” (that deep brown color), they may not be firing at all; this may indicate an ignition or fuel delivery problem in the cylinder(s) they came from. Again, see your dealer before running the engine again.