NGK TR5 V-Power Spark Plugs - 2238

NGK TR5 V-Power Spark Plugs - 2238

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Part Number: 41-TR5

NGK TR5 V-Power Spark Plug – 2238

The NGK TR5 V-Power Spark Plug, stock number 2238, is a proven ignition choice for a variety of GM-based marine engines from Indmar, MerCruiser, Crusader, Marine Power, and Kodiak. Designed to provide dependable spark delivery under demanding operating conditions, the TR5 helps maintain quick starting, smooth idle quality, responsive acceleration, and consistent power throughout the RPM range.

NGK's V-Power design uses a V-cut center electrode that moves the spark toward the outer edge of the firing surface. This promotes efficient ignition of the air-fuel mixture while helping reduce quenching. A copper core provides effective heat transfer, while the resistor construction minimizes electrical interference with sensitive onboard electronics.

Spark plugs are exposed to thousands of combustion cycles, and normal electrode wear or deposits can eventually lead to misfires, hesitation, rough running, difficult starting, and reduced performance. Installing fresh NGK 2238 plugs during scheduled maintenance is an easy way to help keep a compatible marine engine operating as intended.

Spark Plug Specifications

  • Manufacturer: NGK

  • Part Number: TR5

  • NGK Stock Number: 2238

  • Series: V-Power

  • Plug Type: Resistor

  • Center Electrode: V-cut nickel alloy

  • Center Electrode Core: Copper

  • Heat Range: 5

  • Thread Diameter: 14 mm

  • Thread Reach: 17.5 mm

  • Hex Size: 16 mm / 5/8"

  • Seat Type: Tapered

  • Preset Gap: 1.0 mm / approximately .040"

  • Sold Individually

Common Indmar Engine Applications

The NGK TR5 / 2238 is used in select Indmar GM-based marine engines, including:

  • Indmar 5.7L V8 Small Block – Except LS1

  • Indmar 5.7L TBI

  • Indmar 5.7L EFI

  • Indmar 5.7L MPI

  • Indmar Assault 5.7L

  • Indmar Assault 325

  • Indmar 350 CID V8

  • Indmar 7.4L V8 GM Big Block

  • Select Indmar 454 CID applications

NGK specifically catalogs the TR5 for Indmar 5.7L V8 small-block engines, excluding the LS1, from 1994–2005. It is also listed for select 7.4L GM big-block applications.

Common Supra Boat Applications

Compatible Indmar 5.7L engines were installed in numerous Supra inboard boats. Depending on model year and original engine package, applications may include:

  • Supra Launch

  • Supra Launch 20

  • Supra Launch 21V

  • Supra Launch 22SSV

  • Supra Launch 24SSV

  • Supra Sunsport

  • Supra Sunsport 22V

  • Supra Comp

  • Supra Legacy

  • Supra Santera

  • Supra Gravity Games Edition models

Common Moomba Boat Applications

The TR5 may also be used in compatible Indmar-powered Moomba boats, including:

  • Moomba Outback

  • Moomba Outback LS

  • Moomba Outback V

  • Moomba Mobius

  • Moomba Mobius LS

  • Moomba Mobius LSV

  • Moomba Mobius XLV

  • Moomba Kamberra

Common Malibu Boat Applications

Indmar GM-based engines using this spark plug can also be found in select Malibu models, including:

  • Malibu Response

  • Malibu Response LX

  • Malibu Sunsetter

  • Malibu Sunsetter LXi

  • Malibu Wakesetter

  • Malibu Wakesetter VLX

  • Malibu Wakesetter 21 XTi

  • Malibu Wakesetter 23 LSV

  • Malibu Sunscape

Common MasterCraft Applications

Depending on year and installed Indmar engine, potential MasterCraft applications include:

  • MasterCraft ProStar 190

  • MasterCraft ProStar 205

  • MasterCraft X-5

  • MasterCraft X-7

  • MasterCraft X-9

  • MasterCraft X-10

  • MasterCraft X-30

  • MasterCraft MariStar 210

  • MasterCraft MariStar 230

MerCruiser Engine Applications

The NGK TR5 is also specified for select MerCruiser power packages, including:

  • MerCruiser 350 MAG MPI

  • MerCruiser 350 MAG MPI Gen+

  • MerCruiser 350 MAG MPI Horizon

  • MerCruiser 6.2L Black Scorpion MX

  • Select MerCruiser GM small-block V8 applications

A notable application is the MerCruiser 350 MAG MPI from the 2000–2006 period, where NGK catalogs TR5 stock #2238 as the standard replacement plug.

Other Marine Engine Applications

Additional verified or commonly cataloged marine applications include:

  • Crusader 5.7L Plus EFI

  • Crusader 5.7L Plus MPI

  • Crusader 7.4L MPI

  • Marine Power 5.0L / 305 CID V8

  • Marine Power 5.7L / 350 CID GM Small Block

  • Kodiak 5.7L / 350 CID V8

  • Select Volvo Penta GM-based marine engines

Key Features

  • Genuine NGK TR5 V-Power spark plug

  • NGK stock number 2238

  • Popular replacement for GM-based inboard marine engines

  • V-cut center electrode promotes efficient ignition

  • Copper core provides effective heat dissipation

  • Resistor construction helps reduce electrical interference

  • Supports reliable starts and smooth acceleration

  • Helps maintain efficient combustion under load

  • Suitable for select Indmar, MerCruiser, Crusader, Marine Power, and Kodiak engines

  • Excellent choice for seasonal tune-ups and preventative maintenance

Proven Choice for Indmar-Powered Towboats

The NGK TR5 is particularly relevant to owners of older Indmar-powered wake and ski boats. GM-based 5.7L Indmar engines were widely used by Supra, Moomba, Malibu, and MasterCraft during this period, making the TR5 an important service item for many classic towboats still on the water today.

Whether you're maintaining a Supra Launch, Moomba Mobius LSV, Malibu Wakesetter, MasterCraft ProStar, or another boat equipped with a compatible Indmar engine, the NGK TR5 V-Power Spark Plug – 2238 provides proven ignition performance and dependable NGK quality.

Fitment Note: Boat manufacturers frequently offered several engine packages within the same hull and model year. Engine displacement alone may not confirm compatibility either. Always verify NGK TR5 / stock #2238 against your engine model, production year, serial number, service manual, or original spark plug before ordering.