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Marine & Outboard Spark Plugs

NGK Nickel Spark Plug BR6FS (4323)

SKU: GB-BR6FS

$8.80
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The NGK BR6FS (Stock No. 4323) is a standard resistor spark plug widely used in marine petrol engines, including selected MerCruiser, Volvo Penta and Yamaha sterndrive applications. Featuring a nickel electrode, copper core, tapered seat and built-in resistor, the BR6FS provides reliable ignition, efficient heat transfer and reduced electrical interference for dependable marine engine performance.

Key benefits

Key Benefits

  • - Copper-core construction provides efficient heat dissipation.
  • - Nickel centre and ground electrodes.
  • - Built-in resistor helps suppress electrical and radio-frequency interference.
  • - Tapered seat requires no sealing washer.
  • - Compact 16 mm / 5/8" hex.
  • - Corrosion-resistant construction suited to marine applications.
  • - NGK heat range 6.
  • - Suitable for numerous older petrol inboard and sterndrive engines.

Specifications & Dimensions

  • - Brand: NGK
  • - Part Number: BR6FS
  • - NGK Stock Number: 4323
  • - Spark Plug Type: Standard resistor
  • - Thread Diameter: 14 mm / 0.551"
  • - Thread Size: M14 × 1.25
  • - Thread Pitch: 1.25 mm / 0.049"
  • - Thread Reach: 11.2 mm / 0.441" according to NGK application data
  • - Hex / Spanner Size: 16 mm / 5/8"
  • - Factory Spark Gap: 0.8 mm / 0.031"
  • - NGK Heat Range: 6
  • - Seat Type: Tapered / conical
  • - Resistor: Yes
  • - Resistance: Approximately 5 kΩ
  • - Centre Electrode: Nickel
  • - Centre Electrode Core: Copper
  • - Electrode Projection: Non-projected
  • - Ground Electrode: Nickel
  • - Ground Electrodes: 1
  • - Terminal: Solid
  • - Sealing Washer: None – tapered seat

Compatible Marine Engines

  • MerCruiser
  • - MerCruiser 120 GM 153 I/L4 – 1972–1986
  • - MerCruiser 140 GM 181 I/L4 – 1972–1986
  • - MerCruiser 165 – 1971–1981
  • - MerCruiser 2.5L GM 153 I/L4
  • - MerCruiser 3.0L GM 181 I/L4
  • - MerCruiser 175 HP V6
  • - MerCruiser 185 HP V6
  • - MerCruiser 205 HP V6
  • - MerCruiser 4.3L
  • - MerCruiser 4.3LX
  • - MerCruiser 5.0L
  • - MerCruiser 5.7L
  • - MerCruiser 5.7LX
  • - MerCruiser 5.7L EFI
  • - MerCruiser 350 MAG
  • - MerCruiser 350 MAG EFI
  • - MerCruiser 454 MAG
  • - MerCruiser 454 MAG EFI
  • - MerCruiser 454 MAG MPI
  • - MerCruiser 7.4L
  • - MerCruiser 7.4L Alpha
  • - MerCruiser 7.4L Bravo
  • - MerCruiser 7.4L MPI
  • - MerCruiser 7.4L MPI MIE – selected 1995–1997 applications
  • - MerCruiser 8.2L MIE – selected 1990–1996 applications
  • - MerCruiser 502 MAG – 1990–1993
  • - MerCruiser 502 MAG EFI
  • - MerCruiser 502 MAG MPI

Volvo Penta

  • - Volvo Penta AQ175A
  • - Volvo Penta AQ290B
  • - Volvo Penta 740A

Yamaha Marine

  • - Yamaha Stern Drive 3.0L L4
  • - Yamaha Stern Drive V6
  • - Yamaha Stern Drive V8
  • - Yamaha Z-Drive Inline 4
  • - Yamaha Z-Drive V6
  • - Yamaha Z-Drive V8

Cross-Reference Part Numbers

  • - NGK: BR6FS
  • - NGK Stock No.: 4323
  • - Mercury / MerCruiser: 33-59571
  • - Mercury: 59571
  • - Mercury: 898264
  • - Mercury: 898264001
  • - Mercury: 803991
  • - Mercury: 8M0176614
  • - Mercury: 8M2005041
  • - Yamaha: 94701-00365-00
  • - Champion: RV8C
  • - BRP: 0771773

Important Fitment Information

  • BR6FS uses a 14 mm thread, short 11.2 mm reach and tapered seat. Do not substitute it solely because another plug has the same thread diameter. Confirm the engine model, year/serial number, thread reach, seat type, heat range and specified electrode gap.
  • The required gap can also vary by engine application even though BR6FS is supplied at approximately 0.8 mm.

Signs the Spark Plug Needs Replacing

  • - Difficult starting
  • - Rough or inconsistent idle
  • - Engine misfire
  • - Hesitation under acceleration
  • - Reduced engine power
  • - Increased fuel consumption
  • - Carbon or oil fouling
  • - Excessive electrode erosion
  • - Corrosion
  • - Cracked or damaged ceramic insulator

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