# TR6IX NGK Iridium Spark Plug | Genuine NGK Spark Plug

## 🔧 Product Description

**NGK Iridium Spark Plug – Part Number: TR6IX**

Iridium NGK spark plugs offer a longer service life than a standard nickel-tipped spark plug: while nickel-alloy plugs offer a service life of roughly 20,000-40,000km, NGK Iridium IX spark plugs offer a service life of up to 60,000km, so fewer replacements are needed over time despite the higher initial cost.

Precious-metal spark plugs like the NGK Iridium IX also offer higher ignitability, achieved with an exposed fine-tip centre electrode that promotes superior flame growth compared with a standard spark plug. Iridium has a much higher melting point (2410°C) than nickel (1453°C), allowing the centre electrode diameter to be reduced from 2.5mm to 0.6mm – a smaller electrode mass that reduces the impedance to flame progress, helping acceleration, fuel consumption and idle quality.

## ⚙️ Key Features

-   Fine iridium-tipped centre electrode for a slow wear rate and stable idle
-   Longer service life than standard nickel plugs
-   Trivalent metal plating provides superior anti-corrosion and anti-seizing properties
-   Corrugated ribs reduce the risk of flashover
-   Pure alumina silicate ceramic insulator, providing superior strength and better heat transfer
-   Copper core aids in heat removal
-   Triple seals prevent leakage

## 📏 Specifications

-   NGK stock number: 3689
-   Thread: 14 mm
-   Reach: .708"
-   Hex: 16 mm (5/8 in)
-   Seat: Tapered
-   Terminal: Solid
-   Type: Projected

## 🚘 Application

Listed in NGK's application charts for marine, motorcycle, ATV and snowmobile equipment and automotive vehicles. The chart shows a 1.0 mm gap for these engines, but check it against your engine's manual before fitting.

-   Indmar 5.7L V8 CARB H.O. (8 CYL GM SMALL BLOCK) – Inboard Engine
-   Indmar 5.7L V8 EFI H.O. (8 CYL GM SMALL BLOCK) – Inboard Engine
-   Indmar 5.7L V8 GEN 1+ CARB (8 CYL GM SMALL BLOCK) – Inboard Engine
-   Indmar 5.7L V8 GEN 1+ H.O. CARB (8 CYL GM SMALL BLOCK) – Inboard Engine
-   Indmar 5.7L V8 GEN 1+ H.O. PFI (8 CYL GM SMALL BLOCK) – Inboard Engine
-   Indmar 5.7L V8 LT-1 (8 CYL GM SMALL BLOCK) – Inboard Engine
-   Indmar 7.4L V8 (8 CYL GM BIG BLOCK, 1999-1998) – Inboard Engine
-   Indmar 7.4L V8 H.O. (8 CYL GM BIG BLOCK, To 1997) – Inboard Engine
-   Indmar 8.2L V8 (8 CYL GM BIG BLOCK, 1999-1998) – Inboard Engine
-   Indmar FORD 5.8L V8 285 H.O. (351 CID, 1997-1991) – Inboard Engine
-   Marine Power L4 3.0L (181 CID, TAPER SEAT .708 REACH, 2000-1992) – Inboard Engine
-   Marine Power V8 5.7L PREMIUM (350 CID, 1997-1992) – Inboard Engine
-   Marine Power V8 7.4L (L29) (454 CID, 2000) – Inboard Engine
-   Mercruiser 3.0L TKS (4 CYL GM) – Inboard Engine
-   Mercruiser 3.0LX (4 CYL GM) – Inboard Engine
-   Mercruiser 4.3L EFI GEN+ (6 CYL GM V-6, FROM 0L012009) – Inboard Engine
-   Mercruiser 4.3L GEN+ (6 CYL GM V-6, FROM 0L010065) – Inboard Engine
-   Mercruiser 4.3LH EFI GEN+ (6 CYL GM V-6, FROM 0L010044) – Inboard Engine
-   Mercruiser 4.3LX GEN+ (6 CYL GM V-6, 0F803000 TO 0L000000) – Inboard Engine
-   Mercruiser 4.3LXH GEN+ (6 CYL GM V-6, 0F803000 TO 0L000000) – Inboard Engine
-   Mercruiser 5.0L EFI GEN+ (8 CYL GM SMALL BLOCK, FROM 0L015751) – Inboard Engine
-   Mercruiser 5.0L GEN+ (8 CYL GM SMALL BLOCK, FROM 0L015751) – Inboard Engine
-   Mercruiser 5.7L COMP GEN+ (8 CYL GM SMALL BLOCK, FROM 0L002005) – Inboard Engine
-   Mercruiser 5.7L EFI GEN+ (8 CYL GM SMALL BLOCK, FROM 0L010035) – Inboard Engine
-   Mercruiser 5.7L GEN+ (8 CYL GM SMALL BLOCK, FROM 0L010037) – Inboard Engine

That is the 25 most common of 76 applications NGK's charts list for this plug – ask us to check yours.

## 🔄 Supersession & Cross Reference

NGK's cross-reference tables list this plug against these part numbers.

-   DENSO: 4714, 5326, IT20, IT20TT, T20ERR-U
-   ACDelco: 12571165, 41-104, 41-812, 92143446
-   Bosch: 9608, H7LDCR, HR6KII33X
-   Torch: Q6RTP-11

## 📦 Condition

-   Brand new genuine product
-   Supplied in original packaging

## Details

- **Price:** 41.0 AUD
- **Vendor:** NGK
- **Type:** Ignition & Controls

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 41.00 AUD | In stock |

## Images

- TR6IX NGK iridium spark plug
- TR6IX NGK iridium spark plug firing end

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/tr6ix-ngk-iridium-spark-plug-genuine-ngk-spark-plug)
> Updated: 2026-09-03