The NGK BR8HS-10 outboard spark plug comes gapped at 1.0 mm, and that's what the "-10" means. It has a 14 mm thread, 12.7 mm (1/2 in) reach, a 20.8 mm hex and heat range 8. NGK Australia lists it for Suzuki, Yamaha, Tohatsu and Nissan outboards. We sell it as an NGK BR8HS-10 6-pack.
Got a Mercury or Johnson? NGK Australia's part finder doesn't list this plug for either make, so read the number on your old plug first. If you only needed the size, the table has it.
NGK BR8HS-10 specs
| Spec | BR8HS-10 |
|---|---|
| Thread diameter | 14 mm |
| Thread reach (length) | 12.7 mm (1/2 in) |
| Hex (spanner size) | 20.8 mm |
| Electrode gap (as supplied, NGK's figure) | 1.0 mm (0.039 in) |
| Heat range | 8 |
| Resistor | Yes |
| Iridium version (NGK's listed option) | BR8HIX |
Source: NGK's part finder entry for the BR8HS-10 (thread, reach, hex, gap), NGK's part number chart (heat range, resistor) and NGK Spark Plugs Australia's marine part finder (gap and iridium option), all read 12 October 2026. See Sources.
What does the -10 mean in BR8HS-10?
NGK's part number chart reads the BR8HS-10 like this:
- B: 14 mm thread with a 20.8 mm hex.
- R: resistor, which suppresses ignition noise.
- 8: heat range. NGK's chart runs from hot (low numbers) to cold (high numbers).
- H: 12.7 mm thread length (reach).
- S: standard type.
- -10: a 1.0 mm spark gap. A -11 would be 1.1 mm.
So a BR8HS and a BR8HS-10 share the same letters and heat range. The suffix sets the gap.
Which outboards NGK lists the BR8HS-10 for
NGK Spark Plugs Australia's marine part finder lists the BR8HS-10 as the plug for 89 entries, every one at a 1.0 mm gap (read 12 October 2026): 34 Suzuki, 25 Yamaha, 21 Tohatsu and 8 Nissan outboards, plus one personal watercraft. Some of them:
| Make | Models NGK lists with a BR8HS-10 |
|---|---|
| Suzuki | DT40C, DT50C, DT60C, DT75, DT85C, DT90, DT115S, DT140, DT150, DT200, DT225 |
| Yamaha | 40Y, 50G, E65A Enduro, 115C, 175D, 200F, 225D, 250A |
| Tohatsu | M45A/A2, M50D, M60C, M70C, M90A, M115A2, M140A |
| Nissan | NS 50D, NS 60C, NS 70C, NS 90A, NS 120A, NS 140A2 |
Most model lines carry years or a version in NGK's list, and the same model name can appear on more than one row, so check yours in NGK Australia's part finder (see Sources). NGK notes 21 of the 25 Yamaha entries as two-stroke.
The same finder lists the BR8HS-10 for no motorcycle, ATV, snowmobile or commercial and industrial engine. NGK Australia says its listings are "considered under normal conditions of use, fitted by a professional".
Mercury and Johnson outboards: check the plug number first
Our listing says the BR8HS-10 fits "selected marine outboard motors - Yamaha, Mercury and Johnson" and asks you to check your spark plug number. That check matters, because NGK Australia's part finder lists the BR8HS-10 for no Mercury, Mariner, Johnson or Evinrude entry.
What NGK does list for those makes:
- Mercury: NGK's cross-reference matches the Mercury/MerCruiser plug number 33-824406 8 (as NGK prints it) to the BR8HS-10. Across its Mercury entries the finder lists many different plugs. Among them are the BR8HS on five V-200 to V-250 entries (gapped 0.9 or 1.0 mm by model) and the BU8H on 14 entries from the V-135 to the V-300.
- Johnson and Evinrude: the finder lists other plugs, such as the BZ7HS-10, BPZ8HS-10 and BR7HS, and no BR8HS-10.
If your old plug or owner's manual says BR8HS-10, or the Mercury number above, this is the plug. If it says something else, match that number.
BR8HS vs BR8HS-10, BR7HS-10 and BR9HS-10
- BR8HS: the same plug code without a gap suffix. NGK Australia lists it for different engines, mostly personal watercraft (jet skis), mostly at 0.7 mm.
- BR7HS-10: one step hotter. NGK Australia lists it for 64 Tohatsu, Yamaha, Nissan and Suzuki outboard entries.
- BR9HS-10: one step colder, listed for 12 Yamaha entries.
The heat range isn't a free choice. Too cold a plug runs too cool, so deposits build up on the firing end and it can lose its spark. Too hot a plug can cause pre-ignition, which NGK warns can melt the electrodes and damage the piston. Fit the heat range your engine lists.
How to check which plug your outboard takes
- Read the number on the old plug's insulator, or look in your owner's manual.
- Look the engine up in NGK Australia's part finder by make, model and year.
- Match the letters and the heat range, not just the thread. A BU8H screws into the same 14 mm thread but has a different firing end (NGK's U type: surface or semi-surface gap), and NGK lists it for different engines.
- Check the gap your manual gives. NGK says in most cases the gap is set at the factory to suit its catalogue application, but some engines need a different one.
- For fitting, NGK's first installation step is checking that the thread reach is right for the engine. Follow your outboard maker's manual, or have a marine mechanic fit them.
Which Bearings Express product fits
- Pick the NGK BR8HS-10 6-pack if your old plug, your manual or NGK's part finder says BR8HS-10.
- Pick the NGK BU8H 6-pack if your Mercury, Johnson or Evinrude takes a BU8H. Our listing names Mercury plug numbers 12183, 136862 and 13686Q, and Johnson and Evinrude numbers 0503703 and 0509579. NGK Australia's finder lists the BU8H for Mercury V-series engines, so Johnson and Evinrude owners should match the number on the old plug.
- Servicing the boat trailer too? Our marine trailer bearing kits include pairs for Holden axles (LM67048 and LM11949, pair) and Ford axles (L68149 and LM12749, pair).
Both plug packs are in ignition and electrical.
Questions people also ask
What is the gap on a BR8HS-10?
1.0 mm (0.039 in), as supplied. NGK Australia lists 1.0 mm for every BR8HS-10 outboard entry, but your owner's manual has the final word.
What's the difference between BR8HS and BR8HS-10?
The gap suffix. Both are 14 mm, heat range 8 resistor plugs, but NGK Australia lists them for different engines and gaps, so buy the one your engine lists.
Do Mercury outboards take a BR8HS-10?
NGK Australia's finder lists no Mercury model for it. Its cross-reference matches one Mercury/MerCruiser plug number (33-824406 8) to the BR8HS-10, so go by the number on your old plug.
What is the Denso equivalent of a BR8HS-10?
NGK Australia's cross-reference matches the Denso TR24-10 and W24FSR-U10. NGK calls its cross-reference "a guide only".
Is there an iridium BR8HS-10?
NGK Australia lists the BR8HIX as the iridium option for every BR8HS-10 entry. We don't list it.
Related reading
- NGK BPMR7A spark plug: gap, thread size and what it fits
- Holden or Ford trailer bearings? How to tell
- Trailer wheel bearing kits
Sources
- NGK Spark Plugs Australia, part finder, marine (and the motorcycle, ATV, snowmobile, and commercial and industrial sections) (ngk.com.au/partfinder), read 12 October 2026.
- NGK Spark Plugs Australia, spark plug cross-reference (ngk.com.au, and ngk.com.au/crossref.pdf pp. 111, 122 and 150), read 12 October 2026.
- NGK Spark Plugs Australia, technical information: Heat Range, Electrode Gap, Installation and Resistor Spark Plugs (ngk.com.au/technical_info), read 12 October 2026.
- Niterra EMEA, NGK part finder entry for the BR8HS-10 (Tohatsu M50D page, ngkntk.com), read 12 October 2026.
- Niterra EMEA, NGK Spark Plugs and Glow Plugs 2017/2018 catalogue, "How to read our part number" (PDF p. 4) (ngkntk.com), read 12 October 2026.
Checked against NGK Spark Plugs Australia's part finder, cross-reference and technical pages, NGK's part number chart and our own product listings on 12 October 2026.
0 comments