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Marine & Outboard Spark Plugs

NGK Nickel Spark Plug BR7HS (4122)

SKU: GB-BR7HS

$8.80
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The NGK BR7HS (Stock No. 4122) is a resistor-type nickel spark plug used extensively in selected 2-stroke outboard motors. Featuring an M14 × 1.25 thread, 12.7 mm reach and typically a 0.7 mm application gap, its copper-core centre electrode provides reliable ignition and efficient heat transfer. The resistor construction helps suppress electrical interference, making BR7HS suitable for many Tohatsu, Yamaha/Mariner, Suzuki, Mercury and Johnson/Evinrude applications.

Key benefits

Key Benefits

  • - Resistor-type spark plug for reduced electrical/RFI interference
  • - Standard nickel electrode construction
  • - Copper-core centre electrode
  • - NGK heat range 7
  • - Short 12.7 mm / 1/2" reach
  • - Flat gasket seat
  • - Standard non-projected electrode
  • - Common marine 2-stroke spark plug
  • - Suitable for numerous older outboard applications
  • - BR7HIX is the corresponding NGK Iridium reference in application data.

Specifications & Dimensions

  • - Brand: NGK
  • - Part Number: BR7HS
  • - NGK Stock Number: 4122
  • - Spark Plug Type: Standard resistor
  • - Thread Diameter: 14.0 mm / 0.551"
  • - Thread Size: M14 × 1.25
  • - Thread Pitch: 1.25 mm / 0.049"
  • - Thread Reach: 12.7 mm / 0.500"
  • - Hex / Spanner Size: 20.8–21 mm / 13/16"
  • - Typical Application Gap: 0.7 mm / 0.028"
  • - NGK Heat Range: 7
  • - Seat Type: Flat / gasket
  • - Resistor: Yes
  • - Resistance: approximately 5 kΩ
  • - Electrode Type: Standard / non-projected
  • - Centre Electrode: Nickel with copper core
  • - Ground Electrode: Nickel
  • - Ground Electrodes: 1

Compatible Outboard Motors

  • Tohatsu Outboards
  • - M3.5A – 3.5 HP – selected models
  • - M5A2 – 5 HP
  • - M8A – 8 HP
  • - M9.8A – 9.8 HP
  • - M12A – 12 HP
  • - M12B – 12 HP
  • - M15A – 15 HP
  • - M18A – 18 HP
  • - M20A2 – 20 HP
  • - M25A2 – 25 HP
  • - M25B – 25 HP
  • - M25C – 25 HP
  • - M35A – 35 HP
  • - M35B – 35 HP
  • - M35C – 35 HP
  • - M40A – 40 HP

Yamaha Outboards

  • - Yamaha 4 HP
  • - Yamaha 5 HP
  • - Yamaha 30 HP
  • - Yamaha C20
  • - Yamaha C25
  • - Yamaha C30
  • - Yamaha E48
  • - Yamaha LX150
  • - Yamaha PX150
  • Exact model and production year should be confirmed because Yamaha used several similar B7/BR7-series plugs.

Mariner Outboards

  • - 3.5 – 642
  • - 4A – 6E0
  • - 5A – 661
  • - 5C – 6E3
  • - 8B – 677
  • - Marathon 8 – 677
  • - W8 – 677
  • - 9.9C – 682
  • - 15 Marathon – 684
  • - 15A – 651
  • - 15C – 684
  • - W15 – 662
  • - 20C – 6A9
  • - 25 Marathon – 648 / 694 / 695
  • - 25A
  • - 25B
  • - 25C
  • - K25 – 6A4
  • - W25
  • - WS25
  • - 28 – 664
  • - 30 Marathon – 698B
  • - 30A – 689
  • - W30 – 689A / 689B
  • - 40 Marathon – 6F6
  • - K40 – 6F5
  • - W40 – 6F6
  • - 48 – 670
  • - W48 – 670

Mercury Outboards

  • - Mercury 110
  • - Mercury 200
  • - Mercury 350
  • - Mercury 500M
  • - Mercury 500S
  • - Mercury 650S
  • - Mercury 950
  • - Mercury 1100
  • These are older model designations rather than simply horsepower ratings, so engine identification should be checked carefully.

Suzuki Outboards

  • - Suzuki DT15
  • - Suzuki DT16
  • - Suzuki DT20
  • - Spirit / Suzuki – selected models

Evinrude Outboards

  • - 9.9 HP 2-stroke – 1977–2001
  • - 10 Commercial – 1994–2003
  • - 15 Commercial – 1994–2001
  • - 15 HP 2-stroke – 1994–1998
  • - 18 HP Jet – 1995–1998
  • - 20 HP – selected 1978–1998 models
  • - 25 HP – selected 1977–1998 models
  • - 30 HP – selected 1978–1998 models
  • - 65 HP Jet CV4 – 1992–1997
  • - 80 HP Jet CV4 – selected models
  • - 85 HP V4 Backtroller – 1994–1995
  • - 90 HP TurboJet CV4 – 1994–1997
  • - 90 HP CV4 – 1979–1998
  • - 100 HP V4 – selected models
  • - 110 HP CV4 – 1979–1997
  • - 112 HP CV4 – 1979–1997
  • - 115 HP CV4 – 1979–1998

Johnson Outboards

  • - 9.9 HP
  • - 10 HP
  • - 15 HP
  • - 18 HP
  • - 20 HP
  • - 25 HP
  • - 28 HP
  • - 30 HP
  • - 40 HP
  • - 50 HP
  • - 55 HP
  • - 65 HP
  • - 85 HP
  • - 88 HP
  • - 100 HP
  • - 110 HP
  • - 112 HP
  • - 115 HP
  • - 125 HP
  • Exact model/year should be checked before purchase.

Cross-Reference / OEM Part Numbers

  • - NGK: BR7HS
  • - NGK Stock No.: 4122
  • - NGK Iridium: BR7HIX
  • - Yamaha: 94702-00272
  • - Yamaha: 94701-00110
  • - Mariner / Mercury: 33-53098
  • - Mercury / Mariner: 33-8M0114739
  • - Mercury / Mariner: 8M0114739

Important Fitment Information

  • BR7HS is not the same as BR7HS-10. BR7HS applications commonly specify approximately 0.7 mm / 0.028", while BR7HS-10 denotes the 1.0 mm nominal-gap version.
  • This difference matters on Tohatsu engines. For example, application data specifies BR7HS at 0.7 mm for older M5A2, M8A, M9.8A, M25B/M25C and M35-series engines, while later engines can specify B7HS-10 or BR7HS-10.

Signs the Spark Plug Needs Replacing

  • - Difficult starting
  • - Rough or unstable idle
  • - Intermittent misfire
  • - Reduced engine power
  • - Poor acceleration
  • - Increased fuel consumption
  • - Carbon or oil fouling
  • - Worn or rounded electrodes
  • - Excessive electrode gap
  • - Corrosion
  • - Cracked ceramic insulator

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