NGK 2238 TR5 Spark Plug, Surface Discharge, Copper Core, 14mm Thread, Resistor

The NGK 2238 (TR5) is a standard spark plug built on proven NGK technology for reliable, consistent ignition performance. It uses a surface discharge ground configuration paired with a solid copper core center electrode, delivering superior heat dissipation, strong conductivity, and a broad heat range for stable combustion. The ground electrode core and center electrode tip are both nickel, a durable, corrosion-resistant construction that has served as an OE cornerstone for decades of dependable use. The plug body is treated with corrosion-resistant plating, which keeps threads from seizing and makes installation and removal straightforward even after extended service.

The NGK 2238 features a 14mm thread with a tapered seat design and a resistor-type build (5k Ohm resistance) to help suppress ignition noise. It is intended as a direct replacement for the original equipment plug it matches in a spark plug service or tune-up, and is commonly used in Mercury outboard engine applications. Always confirm the correct spark plug against your engine and maintenance manual, and use only as recommended by your engine's original equipment manufacturer, since installing the wrong plug can reduce performance, hurt fuel economy, or damage the engine.

Specifications

• Brand: NGK
• Manufacturer Part Number: 2238
• Spark Plug Type: Standard
• Ground Configuration: Surface Discharge
• Ground Electrode Core Material: Nickel
• Center Electrode Core Material: Copper
• Center Electrode Tip Material: Nickel
• Resistance: 5k Ohm
• Thread Size: 14mm
• Seat Type: Tapered Seat
• Reach: 0.708 inch
• Package Dimensions: 3.98 inches L x 0.91 inches W x 0.86 inches H
• Weight: 0.15 pounds
• UPC: 087295122389

Fitment

Commonly used in Mercury outboard engine spark plug applications. Always check your engine and maintenance manual to confirm this is the correct spark plug for your specific engine before ordering.

Frequently Asked Questions

What type of spark plug is the NGK 2238? The NGK 2238 (TR5) is a standard resistor-type spark plug with a surface discharge ground configuration and a solid copper core center electrode, designed for reliable, consistent ignition performance.

What is the thread size and seat type of the NGK 2238 spark plug? It has a 14mm thread with a tapered seat design, and a reach of 0.708 inch.

What materials are used in the NGK 2238 spark plug? The ground electrode core and center electrode tip are nickel, while the center electrode core is copper, giving the plug strong heat dissipation and conductivity.

Is the NGK 2238 a resistor spark plug? Yes, the NGK 2238 has a resistance rating of 5k Ohm, which helps suppress ignition noise.

How much does the NGK 2238 spark plug weigh? The NGK 2238 spark plug weighs 0.15 pounds.

What engines is the NGK 2238 spark plug used in? The NGK 2238 is commonly used in Mercury outboard engine spark plug applications; always check your engine and maintenance manual to confirm it is the correct plug for your specific engine.

Does the NGK 2238 have corrosion-resistant plating? Yes, the NGK 2238 is treated with corrosion-resistant plating, which makes installation and removal easier even after extended use.

What is the difference between the NGK 2238 and NGK's iridium spark plugs? The NGK 2238 (TR5) is a standard copper-core plug, while NGK also offers iridium versions with a fine-wire iridium center electrode tip for improved starting, idling, and throttle response; those are separate NGK part numbers from the 2238.

What is the package size of the NGK 2238 spark plug? The NGK 2238 ships in a package measuring 3.98 inches long by 0.91 inches wide by 0.86 inches high.

What ground configuration does the NGK 2238 spark plug use? The NGK 2238 uses a surface discharge ground configuration, part of NGK's standard spark plug design.

How do I know if the NGK 2238 is the right spark plug for my engine? Check your engine and maintenance manual for the correct spark plug specification, and only use the NGK 2238 as recommended by your engine's original equipment manufacturer, since an incorrect plug can reduce performance or damage the engine.

Is the NGK 2238 spark plug genuine NGK or aftermarket? The NGK 2238 is a genuine NGK standard spark plug, part of NGK's OE-grade spark plug lineup.