# TR55IX NGK Iridium Spark Plug | Genuine NGK Spark Plug

## 🔧 Product Description

**NGK Iridium Spark Plug – Part Number: TR55IX**

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: 7164
-   Thread: 14 mm
-   Reach: .708"
-   Hex: 16 mm (5/8 in)
-   Seat: Tapered
-   Terminal: Solid
-   Type: Projected, Wide Gap

## 🚘 Application

Listed in NGK's application charts for marine, motorcycle, ATV and snowmobile equipment and automotive vehicles. The chart shows a 1.5 mm gap for these engines, but check it against your engine's manual before fitting.

-   Crusader GM V8-5.0L MP (275 HP, 2005) – Inboard Engine
-   Crusader GM V8-5.7L CARB (300 HP) – Inboard Engine
-   Crusader GM V8-5.7L MP (220 HP, 2005) – Inboard Engine
-   Crusader GM V8-6.0L MP (375 HP) – Inboard Engine
-   Crusader GM V8-8.1L MP (385 HP) – Inboard Engine
-   Crusader GM V8-8.1L MP (HO) (425 HP) – Inboard Engine
-   Indmar 4.6L MPI NORTHSTAR (279 CID) – Inboard Engine
-   Indmar 5.7L V8 LS1 (8 CYL GM SMALL BLOCK, 2002-1994) – Inboard Engine
-   Indmar 5.7L V8 LS1 (8 CYL GM SMALL BLOCK, 2005-2003) – Inboard Engine
-   Indmar 6.0L V8 (8 CYL GM BIG BLOCK, 2005-2003) – Inboard Engine
-   Indmar 8.1L MPI VORTEC (8 CYL GM BIG BLOCK, 2005-2003) – Inboard Engine
-   Mercruiser 4.3L MPI GEN+ (6 CYL GM V-6, FROM 0M322781) – Inboard Engine
-   Mercruiser 4.5L BRIZO (6 CYL V-6) – Inboard Engine
-   Mercruiser 5.0L MPI GEN+ (8 CYL GM SMALL BLOCK, FROM 0M320415) – Inboard Engine
-   Mercruiser 8.1S HO (8 CYL GM BIG BLOCK, 2006-2000) – Inboard Engine
-   Mercruiser 8.1S HORIZON (8 CYL GM BIG BLOCK, 2006-2000) – Inboard Engine
-   Mercruiser 350 MAG MPI GEN+ (8 CYL GM SMALL BLOCK, FROM 0M310000) – Inboard Engine
-   Mercruiser 350 MAG MPI GEN+ (8 CYL GM SMALL BLOCK, FROM 0M320590) – Inboard Engine
-   Mercruiser 350 MAG MPI GEN+ HORIZON (8 CYL GM SMALL BLOCK, FROM 0M310000) – Inboard Engine
-   Mercruiser 496 MAG (8 CYL GM BIG BLOCK) – Inboard Engine
-   Mercruiser 496 MAG HO (8 CYL GM BIG BLOCK) – Inboard Engine
-   Mercruiser BLACK SCORPION 5.7L (8 CYL GM SMALL BLOCK, FROM 0M391852, 2006-2000) – Inboard Engine
-   Mercruiser BLACK SCORPION MX 6.2 (8 CYL GM SMALL BLOCK, FROM 0M391778, 2006-2000) – Inboard Engine
-   Mercruiser MX 6.2 MPI (8 CYL GM SMALL BLOCK, FROM 0M320614, 2006-2000) – Inboard Engine
-   Mercruiser MX 6.2 MPI HORIZON (8 CYL GM SMALL BLOCK, FROM 0M320614) – Inboard Engine

That is the 25 most common of 245 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.

-   ACDelco: 12, 12561466, 12563707, 12565753, 14, 15, 16, 1835342T and 30 more
-   Autolite: XP103, XP104, XP105, XP5243, XP5243DP2, XP5245, XP5245DP2, XP605 and 3 more
-   Bosch: 4041, 4458, 4459, 6241, 9601, 9653, 9655, HR8KII33V and 2 more
-   Beck Arnley: 1765288

## 📦 Condition

-   Brand new genuine product
-   Supplied in original packaging

## Details

- **Price:** 38.0 AUD
- **Vendor:** NGK
- **Type:** Ignition & Controls

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| Default Title | 38.00 AUD | In stock |

## Images

- TR55IX NGK iridium spark plug

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> Source: [Sawley's Auto and Marine](https://www.sawleysautoandmarine.com.au/products/tr55ix-ngk-iridium-spark-plug-genuine-ngk-spark-plug)
> Updated: 2026-09-03