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Marine & Outboard Spark Plugs

NGK Nickel Spark Plug B7HS-10 (2129)

SKU: GB-B7HS-10

$8.80
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The NGK B7HS-10 (Stock No. 2129) is a standard nickel spark plug widely used in selected 2-stroke marine outboard engines. Featuring a copper-core centre electrode, corrosion-resistant metal plating and a 1.0 mm factory gap, it provides reliable starting, consistent combustion and effective heat dissipation. Its short-reach M14 thread and gasket seat suit numerous Yamaha, Mercury/Mariner, Tohatsu, Suzuki and other older outboard applications.

Key benefits

Key Benefits

  • - Standard NGK nickel spark plug
  • - Copper-core centre electrode for efficient heat transfer
  • - Designed for many 2-stroke outboard applications
  • - Trivalent metal plating helps resist corrosion and seizure
  • - Corrugated ceramic ribs help prevent flashover
  • - High-grade alumina ceramic insulator
  • - Triple sealing helps prevent combustion-gas leakage
  • - Factory gap of 1.0 mm
  • - Non-resistor design
  • - NGK heat range 7

Specifications & Dimensions

  • - Brand: NGK
  • - Part Number: B7HS-10
  • - NGK Stock Number: 2129
  • - Spark Plug Type: Standard nickel
  • - Thread Diameter: 14 mm / 0.551"
  • - Thread Size: M14 × 1.25
  • - Thread Reach: 12.7 mm / 0.500"
  • - Hex / Spanner Size: 20.8 mm / 13/16"
  • - Spark Gap: 1.0 mm / 0.039"
  • - NGK Heat Range: 7
  • - Seat Type: Gasket / flat seat
  • - Resistor: No – non-resistor
  • - Centre Electrode: Nickel alloy with copper core
  • - Ground Electrodes: 1

Compatible Outboard Motors

  • NGK's application finder directly confirms B7HS-10 for numerous Yamaha engines, while marine application/cross-reference catalogues identify additional Mercury/Mariner, Tohatsu, Suzuki and OMC applications. Because specifications can change by model code, ignition system and year, horsepower alone should not be used to determine fitment.

Yamaha Outboards

  • - Yamaha 4 HP – selected 2-stroke models
  • - Yamaha 5 HP – selected 2-stroke models
  • - Yamaha 8 HP – selected models including 8MSHB
  • - Yamaha 9.9 HP – selected 2-stroke models
  • - Yamaha 15 HP – selected models including 15MSH
  • - Yamaha 20 HP – selected 2-cylinder 2-stroke models
  • - Yamaha 25 HP – selected 3-cylinder 2-stroke models
  • - Yamaha 30 HP – selected 2-stroke models
  • - Yamaha 40 HP – selected models including 40H and 40C
  • NGK specifically confirms, among others, Yamaha 15MSH (2006–2010), Yamaha 25 HP 3-cylinder (1996–2002), Yamaha 40C 3-cylinder (1997–2002) and Yamaha 40H 698 cc 2-stroke applications.

Mercury Outboards

  • - Mercury 6 HP – selected models
  • - Mercury 8 HP – selected models
  • - Mercury 9.9 HP – selected models
  • - Mercury 15 HP – selected models
  • - Mercury 18 HP – selected models
  • - Mercury 25 HP – selected models
  • - Mercury 30 HP – selected models
  • - Mercury 40 HP – selected models
  • - Mercury 50 HP – selected older models

Mariner Outboards

  • - Mariner 15 Marathon 684 CDI
  • - Mariner 15C 684
  • - Mariner K15 6K4
  • - Mariner K15 6M7
  • - Mariner W15 684
  • - Additional selected Mariner 2-stroke models using the B7HS-10 specification

Tohatsu Outboards

  • - Tohatsu 9.9 HP – selected 2-stroke models
  • - Tohatsu 15 HP – selected 2-stroke models
  • - Tohatsu 18 HP – selected 2-stroke models
  • - Tohatsu 25 HP – selected 2-stroke models
  • - Tohatsu 30 HP – selected 2-stroke models
  • - Tohatsu 40 HP – selected 2-stroke models

Suzuki Outboards

  • - Suzuki 9.9 HP – selected models
  • - Suzuki 15 HP – selected models
  • - Suzuki 25 HP – selected models
  • - Suzuki 30 HP – selected models

Johnson / Evinrude / OMC

  • - Selected Johnson outboards originally specifying the equivalent plug/application
  • - Selected Evinrude outboards
  • - Selected OMC outboards
  • - An application chart specifically lists Evinrude 75 HP for B7HS-10, but model/year should be checked before ordering.

Cross-Reference / OEM Part Numbers

  • - NGK: B7HS-10
  • - NGK Stock No.: 2129
  • - Yamaha: 94701-00217-00
  • - Yamaha: 94702-00217-00
  • - Mercury / Mariner: 33-41263M
  • - Mercury / Mariner: 41263M
  • - Mercury / Mariner: 33-41263B
  • - Mercury / Mariner: 41263B
  • - Johnson / Evinrude / OMC: 509563
  • - Johnson / Evinrude / OMC: 0509563
  • - Suzuki: 09482-00532-000
  • - Tohatsu: 9701-1-1005
  • - Tohatsu: 970111005M

Important Fitment Information

  • B7HS-10 and B7HS should not automatically be treated as identical applications. The “-10” identifies the 1.0 mm nominal gap, whereas applications specifying B7HS may use a different gap. Some Mariner models, for example, specify B7HS while particular CDI versions specify B7HS-10. Always check the engine model, serial/year and manufacturer's specified plug before installation.

Signs the Spark Plug Needs Replacing

  • Common signs include difficult starting, rough idle, misfiring, loss of power, poor acceleration, excessive fuel consumption, carbon or oil fouling, worn electrodes, corrosion, cracked ceramic insulation or an electrode gap outside specification.

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