AC Delco MR43-T Marine Spark Plug | GM V8 Pre-Vortec Engines | Replaces MR44-T, MerCruiser 33-898264001, Crusader 97782, NGK BR6FS, Champion RV8C, OMC 0763819 & Marine Power 0003-015 | Sold Individually

AC Delco MR43-T Marine Spark Plug — GM V8 Pre-Vortec Engines | Replaces AC Delco MR44-T, MerCruiser 33-898264001, Crusader 97782, NGK BR6FS, Champion RV8C, OMC 0763819 & Marine Power 0003-015 | Sold Individually

AC Delco MR43-T is a conventional marine spark plug for GM V8 pre-Vortec engines used in MerCruiser, Crusader, Marine Power, and OMC Cobra stern drive and inboard applications. Short-reach design. Replaces AC Delco MR44-T, MerCruiser 33-898264001, Crusader 97782, NGK BR6FS, Champion RV8C, OMC 0763819, and Marine Power 0003-015. Sold individually — order the quantity needed for your engine.

Part Specifications

• Part Number: AC Delco MR43-T
• SKU: ACD-MR43-T
• Plug Type: Conventional marine spark plug (short-reach)
• Application: GM V8 pre-Vortec marine engines
• Replaces (AC Delco): MR44-T (alternate heat range — see note below)
• Replaces (MerCruiser): 33-898264001
• Replaces (Crusader): 97782
• Replaces (NGK): BR6FS (see also: NGK 4323 BR6FS Spark Plug)
• Replaces (Champion): RV8C
• Replaces (OMC): 0763819
• Replaces (Marine Power): 0003-015
• Sold As: Individually (single plug) — order quantity to match your engine’s cylinder count

Cross-Reference & Replacement Guide

The MR43-T replaces part numbers across several marine engine manufacturers and ignition brands that all specified the same plug for GM V8 pre-Vortec applications:

• AC Delco MR44-T: The MR43-T and MR44-T are related AC Delco marine plugs for the same engine family but with different heat ranges. The MR43-T is a slightly cooler heat range than the MR44-T. Verify which heat range is specified in your engine service manual — do not substitute one for the other without confirming the OEM heat range specification for your engine model and operating conditions.
• MerCruiser 33-898264001: OEM plug number for MerCruiser GM V8 pre-Vortec stern drives and inboards. If your MerCruiser service manual or existing plugs show this number, the MR43-T is the AC Delco replacement.
• Crusader 97782: OEM plug number for Crusader GM V8 pre-Vortec inboard engines. The MR43-T is the AC Delco equivalent.
• NGK BR6FS: The NGK 4323 (BR6FS) is the NGK equivalent for the same application. The MR43-T is the AC Delco alternative to the BR6FS.
• Champion RV8C: Champion marine plug equivalent for the same GM V8 pre-Vortec application. The MR43-T is the AC Delco replacement.
• OMC 0763819: OEM plug number for OMC Cobra stern drives using GM V8 pre-Vortec engines. The MR43-T is the AC Delco replacement for this application.
• Marine Power 0003-015: OEM plug number for Marine Power inboard engines using GM V8 pre-Vortec blocks. The MR43-T is the AC Delco replacement.

GM V8 Pre-Vortec — Engine Applications

The MR43-T is the correct plug for GM V8 engines produced before the Vortec cylinder head redesign. The pre-Vortec small block and big block GM V8 was used across a wide range of marine applications from the 1970s through the early 1990s:

• MerCruiser pre-Vortec V8 stern drives and inboards: Including 5.0L (305 cid), 5.7L (350 cid), 7.4L (454 cid), and 8.2L (502 cid) pre-Vortec small block and big block engines in MerCruiser applications
• Crusader pre-Vortec V8 inboards: Crusader inboard engines using GM V8 pre-Vortec blocks in the same displacement range
• OMC Cobra pre-Vortec V8 stern drives: OMC Cobra stern drives using GM V8 pre-Vortec engines (OMC part 0763819)
• Marine Power pre-Vortec V8 inboards: Marine Power inboard engines using GM V8 pre-Vortec blocks (Marine Power part 0003-015)
• Not for Vortec or later GM V8 engines: Engines produced from the mid-1990s onward with Vortec cylinder heads use a different plug specification. The MR43-T is for pre-Vortec applications only — confirm your engine’s model year and cylinder head type before ordering.
• Verify before ordering: Confirm the MR43-T is the correct plug for your engine model and year by checking your engine service manual or comparing to your existing plug part number.

MR43-T vs MR44-T — Heat Range Note

• The MR43-T and MR44-T are both AC Delco marine plugs for GM V8 pre-Vortec engines, but with different heat ranges. Heat range affects how quickly the plug tip dissipates heat during combustion — the wrong heat range can cause fouling (too cold) or pre-ignition (too hot) in sustained operation.
• The MR43-T is a slightly cooler heat range plug than the MR44-T. Engine manufacturers specify one or the other based on the engine’s compression ratio, fuel system, and typical operating RPM range.
• Do not substitute the MR43-T for the MR44-T (or vice versa) without confirming the OEM heat range specification in your engine service manual. The search boost on this listing includes “MR44-T” as a search term — if your engine specifies MR44-T, verify the correct part before ordering this listing.

Application Notes

• Sold individually — order the quantity matching your engine’s cylinder count (8 plugs for a V8 engine)
• Verify the correct gap specification in your engine service manual before installation
• Thread the plug in by hand for the first several turns to avoid cross-threading; torque to the specification in your engine service manual
• Apply anti-seize to plug threads if specified by your engine manufacturer, particularly on aluminum head applications
• Inspect and replace at the interval specified in your engine service manual; conventional plugs in marine service typically have shorter service intervals than platinum or iridium plugs
• Check plug condition at each service interval — fouling patterns on a conventional plug (oil fouling, carbon fouling, overheating) indicate engine and fuel system conditions that should be investigated

Additional Information

• Vendor: AC Delco
• SKU: ACD-MR43-T
• Part Number: MR43-T
• Replaces: AC Delco MR44-T | MerCruiser 33-898264001 | Crusader 97782 | NGK BR6FS | Champion RV8C | OMC 0763819 | Marine Power 0003-015
• Product Type: Boat & Engine Maintenance / Spark Plugs
• Plug Type: Conventional marine (short-reach)
• Application: GM V8 pre-Vortec marine engines
• Sold As: Individually (single plug)
• Country of Origin: USA
• HS Code: 8511.10 (spark plugs — verify for your import classification)

Frequently Asked Questions

Q: What is the difference between the MR43-T and the MR44-T?
A: Both are AC Delco marine plugs for GM V8 pre-Vortec engines but with different heat ranges. The MR43-T is a slightly cooler heat range. Do not substitute one for the other without confirming the OEM heat range specification in your engine service manual for your specific engine model and operating conditions.

Q: Does the MR43-T replace MerCruiser 33-898264001?
A: Yes — the MR43-T is the AC Delco replacement for MerCruiser 33-898264001, the OEM plug for MerCruiser GM V8 pre-Vortec applications.

Q: Is the MR43-T correct for OMC Cobra engines?
A: Yes — the MR43-T replaces OMC 0763819, the OEM plug for OMC Cobra stern drives using GM V8 pre-Vortec engines. Verify against your OMC service manual for your specific engine model and year.

Q: How many plugs do I need for a GM V8 engine?
A: A V8 engine requires 8 spark plugs. Order 8 individual MR43-T plugs for a full tune-up. This listing is for one (1) plug.

Q: Will the MR43-T work in a Vortec GM V8 engine?
A: No — the MR43-T is for pre-Vortec GM V8 engines only. Vortec engines (mid-1990s and later, identified by the “Vortec” designation on the intake manifold or in the engine documentation) use a different plug specification. Confirm your engine’s cylinder head type and model year before ordering.