The result of these problems is that the temperature in the combustion chamber gets too high. As soon as the temperature in the chamber gets higher than normal the engine begins to run poorly and the damage to the engine begins. Detonation is usually caused by the air/fuel mixture being lean and the erosion of the piston starts at the edge or outer diameter of the piston. If the erosion starts in the center of the piston it is probably an ignition problem. An engine running hot due to deteriorated water pump or cooling system blockage compounds the problem. A Marine Outboard Monitor with its digital 99.5% accuracy can indicate cylinder to cylinder temperature variation and help you avoid costly damage. Try one today. Please stop by again. Thank you for your interest!
Here is a shot of two thermocouples installed under the cylinder head bolts