How to Read Spark Plug Colors (written by Atlantic Jet Sports)
In General: Reading spark plugs can be a valuable tuning aid. By examining the spark plug insulator color, an experienced personal watercraft engine tuner can determine valuable information about the engine's overall operating condition.
Normal: Grey to Light Golden-Brown Color
* This condition is ideal, the spark plug and engine air/fuel mixture are operating properly.
Dry: Black Soot Buildup
* Air/fuel mixture is too rich, the carburetor settings are incorrect, or the flame arrestor is dirty or has mounting problems.
* Spark plug heat range is too cold for the operating conditions.
* Ignition system problems causing a weak or intermittent spark.
Wet Fouling: Shiny, Wet, Black Appearance
* Excessive use of the choke (gas fouled)
* Prolonged low rpm operation (gas or oil fouled)
* Fuel to oil ratio is too rich (oil fouled)
Excess Deposits: Bumpy, Chalky Buildup
* Poor fuel quality
* Oil leakage into combustion chamber
* Improper oil used for premix/injected
Overheated: White, Blistered, Melted Electrode
* Lean air/fuel mixture
* Spark plug heat range is too hot for operating condition of the engine
* Plug is not properly gapped and/or torqued onto head
* Overly advanced timing
A detonation problem would show signs, such as silver specs, black specs, or melting or breakage at the firing tip.
NOTE: Signs of fouling or excessive heat must be traced quickly to prevent further deterioration of performance and to prevent possible engine damage.
In General: Reading spark plugs can be a valuable tuning aid. By examining the spark plug insulator color, an experienced personal watercraft engine tuner can determine valuable information about the engine's overall operating condition.
Normal: Grey to Light Golden-Brown Color
* This condition is ideal, the spark plug and engine air/fuel mixture are operating properly.
Dry: Black Soot Buildup
* Air/fuel mixture is too rich, the carburetor settings are incorrect, or the flame arrestor is dirty or has mounting problems.
* Spark plug heat range is too cold for the operating conditions.
* Ignition system problems causing a weak or intermittent spark.
Wet Fouling: Shiny, Wet, Black Appearance
* Excessive use of the choke (gas fouled)
* Prolonged low rpm operation (gas or oil fouled)
* Fuel to oil ratio is too rich (oil fouled)
Excess Deposits: Bumpy, Chalky Buildup
* Poor fuel quality
* Oil leakage into combustion chamber
* Improper oil used for premix/injected
Overheated: White, Blistered, Melted Electrode
* Lean air/fuel mixture
* Spark plug heat range is too hot for operating condition of the engine
* Plug is not properly gapped and/or torqued onto head
* Overly advanced timing
A detonation problem would show signs, such as silver specs, black specs, or melting or breakage at the firing tip.
NOTE: Signs of fouling or excessive heat must be traced quickly to prevent further deterioration of performance and to prevent possible engine damage.
