How to choose the right spark plug model for outboard motors? A guide to matching calorific value, thread size and electrode gap

1. Heat value matching of marine spark plugs: core indicators determine the heat dissipation capacity of the product
The heat value is the core parameter of the heat dissipation and high temperature resistance of the spark plug, which directly affects the ignition stability and the service life of the engine
The heat value classification of spark plugs: generally divided into 1-9 levels (1-3 is low heat value, 4-6 is medium heat value, 7-9 is high heat value). Spark plugs with low calorific value have slow heat dissipation and are suitable for some low-load marine engines; spark plugs with high calorific value have fast heat dissipation and are suitable for high-speed, high-power outboard engines

2. Selection basis for marine spark plugs:
Two-stroke outboard engine: Due to its high fuel mixture ratio and high machine temperature during combustion, it is recommended to choose spark plugs with high calorific value, which can avoid electrode ablation and increase product service life and operational safety
Four-stroke outboard engine: You can choose medium and low calorific values ​​to balance heat dissipation and anti-carbon deposition requirements
Ambient temperature: In some high-temperature waters, spark plugs with higher calorific values ​​need to be selected, and marine spark plugs with slightly lower calorific values ​​can be selected in cold waters

3. Thread size: Ensure sealing and product compatibility. Whether the thread size is appropriate directly affects the installation adaptability and needs to be strictly matched with the engine cylinder head to ensure the quality of product use. At the same time, the sealing structure also reduces the intrusion of external impurities and pollutants, protects the internal components of the product from damage, and extends the overall service life.
About the measurement method of marine spark plugs:
1. Remove the old spark plug and measure the thread diameter and length
2. Refer to the original manual or consult the brand

4. Electrode gap: affects ignition energy and stability
The electrode gap is the distance between the center electrode and the ground electrode, which needs to be adjusted according to the voltage of the ignition system
Standard range: The common gap of outboard motors is 0.7-1.0mm, which is suitable for medium and low voltage systems; high compression ratio models can be appropriately increased to 1.1mm to enhance the spark intensity