Ive seen some diesel-powered boats emit a gray colored exhaust and others that emit a heavy black exhaust. What causes the difference?
A. The following explanation has been provided by Yanmar Diesel America Corporation of Buffalo Grove, IL. All internal combustion engines emit some type of exhaust smoke during operation. The purpose of this discussion is to familiarize new marine diesel engine owners with what is normal diesel smoke vs. smoke that may be an indication of an engine malfunction. START-UP: When a cold diesel engine is started, the heat of compression is the only energy source available to heat the fuel in the combustion chamber to the temperature necessary to ignite the fuel. Even after the engine has started, the temperature in the combustion chamber may still be too low to support complete combustion. The resulting unburned and partially burned fuel is exhausted as a mist of small droplets that is seen as white smoke (cold smoke). This condition normally lasts for 3-5 minutes. Air and water temperatures also have an affect on cold smoke. The amount and duration of cold smoke will increase or decrease i
