ACDelco MR43T Marine Spark Plug – GM Part #5613438

Replacement Spark Plug for Compatible Marine Inboard Engines

Keep your boat's ignition system properly maintained with the ACDelco MR43T Spark Plug, a replacement spark plug used in select carbureted and throttle body injection (TBI) marine engines.

The ACDelco MR43T, also identified by GM part number 5613438, is commonly used in older inboard marine engine applications, including compatible engines found in tournament ski boats and wakeboard boats.

Designed for engines using pre-Vortec cylinder heads, this spark plug is a replacement option for many carbureted marine engines and certain throttle body injection configurations.

Whether you're performing routine ignition maintenance, replacing worn spark plugs, or servicing an older inboard boat engine, choosing the correct spark plug is important for reliable ignition performance.

For many compatible Indmar marine engine applications, the specified spark plug gap is 0.035 inches. However, the correct gap should always be verified against your particular engine's service specifications before installation.

Important: Spark plugs are sold individually. Price is for one (1) spark plug.

Key Features & Benefits

• ACDelco MR43T Spark Plug: Replacement ignition component for compatible marine engines.
• GM Part #5613438: Identifying part number for replacement and fitment searches.
• Marine Engine Applications: Used in select inboard tournament ski and wakeboard boat engines.
• Carbureted Engine Compatibility: Fits many compatible carbureted marine engine configurations.
• Throttle Body Injection Applications: Used in certain TBI marine engines.
• Pre-Vortec Cylinder Heads: Intended for applicable engines equipped with pre-Vortec cylinder heads.
• Indmar Applications: Used in select Indmar marine engines requiring the MR43T spark plug.
• Common Gap Specification: 0.035" for many applicable Indmar engines; verify before installation.
• Individual Replacement: Sold as one spark plug for maintenance or replacement needs.

Product Specifications

• Brand: ACDelco
• Part Number: MR43T
• GM Part Number: 5613438
• Product Type: Marine Engine Spark Plug
• Application: Compatible Inboard Marine Engines
• Fuel System Compatibility: Select Carbureted and Throttle Body Injection Engines
• Cylinder Head Application: Pre-Vortec
• Common Indmar Spark Plug Gap: 0.035" (Verify for Your Engine)
• Quantity: 1 Spark Plug
• Sold As: Individual Unit

Marine Spark Plug for Carbureted and TBI Engines

The ACDelco MR43T is used in a range of older marine engine applications that require this specific spark plug.

It is commonly associated with carbureted marine engines and certain throttle body injection systems, particularly engines equipped with pre-Vortec cylinder heads.

These applications can include engines installed in tournament ski boats and wakeboard boats.

Because spark plug requirements vary by engine manufacturer, model, and production year, always confirm the MR43T part number before ordering.

ACDelco MR43T Spark Plug Gap

For many Indmar engines requiring the ACDelco MR43T, the commonly specified spark plug gap is:

0.035 inches

The correct gap may vary by engine application.

Always consult your engine's service manual or manufacturer specifications before adjusting or installing the spark plug.

Installation and Maintenance Recommendations

Proper spark plug installation helps protect engine components and supports reliable ignition system operation.

Spark Plug Gap

Check the electrode gap before installation and adjust only when appropriate for the specific spark plug and engine.

Aluminum Cylinder Heads

The supplied application guidance recommends anti-seize compound for certain aluminum cylinder head applications, including applicable Hammerhead and Corvette marine engines.

However, spark plug manufacturers may specify different installation procedures depending on plug construction and thread coatings. Confirm whether anti-seize is recommended for your exact engine and spark plug before applying it.

Dielectric Grease

Appropriate dielectric grease may be applied to the inside of compatible spark plug boots according to the manufacturer's instructions to help prevent the boots from sticking and tearing during future removal.

Installation Torque

Always follow the correct spark plug tightening specifications for your engine and cylinder head material.

Compatible Marine Engine Applications

The ACDelco MR43T may be used in select:

• Indmar marine engines specifying MR43T spark plugs
• Carbureted inboard marine engines
• Throttle body injection (TBI) marine engines
• Pre-Vortec GM-based marine engine configurations
• Tournament ski boat and wakeboard boat engines requiring GM #5613438

Fitment Note: Not all Indmar, GM-based, Hammerhead, Corvette, or other marine engines use this spark plug. Verify the engine's required part number and specifications before purchasing.

What's Included?

• (1) ACDelco MR43T Spark Plug – GM #5613438

SOLD INDIVIDUALLY — ONE SPARK PLUG PER ORDERED UNIT.

For multi-cylinder engine maintenance, order the appropriate quantity based on your engine's spark plug requirements.

Who Is This Spark Plug For?

The ACDelco MR43T Marine Spark Plug is intended for:

• Owners of compatible older inboard ski and wakeboard boats
• Marine technicians servicing carbureted engines
• Owners maintaining select TBI marine engines
• Customers replacing spark plugs in compatible pre-Vortec engines
• Indmar engine owners whose service specifications call for the MR43T

Maintain your compatible marine engine's ignition system with the ACDelco MR43T Spark Plug, available individually from Bakes Marine.

Bakes Resource Library:

• Indmar Spark Plug & Spark Plug Wire Reference Chart (PDF)