NGK Spark Plug BZ7HS-10

Function and Technical Context

The NGK BZ7HS-10 spark plug is the component responsible for generating the electrical spark that initiates combustion in the outboard motor cylinder. It belongs to the ignition system and operates under high temperature and pressure conditions within the combustion chamber, where its central electrode must produce a precise electrical discharge in each engine cycle. A worn electrode or a spark plug with carbon deposits causes ignition misfires, hesitation during acceleration, increased fuel consumption, and difficulty starting the engine, especially in cold conditions. NGK's BZ7HS-10 reference incorporates an electrode gap of 1.0 mm (indicated by the "-10" suffix in NGK nomenclature), making it specific for applications where the engine manufacturer requires this electrode separation to optimize combustion.

When to Replace This Component?

The most common symptoms of a deteriorated spark plug in an outboard motor are hesitation or rough idle, loss of acceleration power, difficult starting, and in advanced cases, complete failure of one or several cylinders. NGK recommends inspecting and checking spark plugs at each annual seasonal maintenance, and replacing them every 100 hours of use or once a year as a preventive measure, which in intensively used engines may mean shorter intervals. Changing spark plugs on a scheduled basis, without waiting for them to fail on the water, is the most economical and reliable practice to ensure safe starting and optimal engine performance.

Equivalent Manufacturer References