NGK V-Power Spark Plug 7558, ZFR5F Equivalent - Fits Mercury EFI 4-Stroke 65-150 HP Outboards

The NGK 7558 is a V-Power spark plug engineered for reliable ignition and consistent performance in Mercury EFI 4-Stroke outboard engines from 65 HP to 150 HP. Built around NGK's ZFR5F design, this resistor plug pairs a copper center electrode core with a nickel ground electrode core to deliver strong, consistent sparking across the engine's operating range. The flat seat design and 14 mm x 1.25 mm thread ensure a precise, gas-tight fit in the cylinder head, while the 0.749 inch reach and 5/8 inch hex size match factory specifications for straightforward installation with a standard spark plug socket.

Rated at 5000 Ohm resistance, the NGK 7558 helps suppress electrical interference that can affect onboard electronics while maintaining dependable ignition timing. The plug ships pre-gapped to 0.32 inches, so it is ready to install without additional adjustment on most applications. As a direct equivalent to Mercury part numbers 33-8M0204728 and 33-8M0057936, it is a straightforward replacement for boat owners servicing compatible Mercury EFI 4-Stroke outboards.

Specifications

• Brand: NGK
• Manufacturer Part Number: 7558
• Product Line: NGK V-Power
• Plug Type: ZFR5F
• Configuration: Resistor
• Thread Size: 14 mm x 1.25 mm
• Reach: 0.749 inches
• Hex Size: 5/8 inch
• Seat Type: Flat
• Ground Electrode Core Material: Nickel
• Center Electrode Core Material: Copper
• Insulator Height: 50.50 mm
• Pre-Gap Size: 0.32 inches
• Resistance: 5000 Ohm
• Weight: 0.15 pounds
• UPC: 087295175583

Fitment

• Mercury EFI 4-Stroke outboard engines, 65 HP to 150 HP

Replaces (OEM)

• Mercury 33-8M0204728
• Mercury 33-8M0057936

Frequently Asked Questions

What is the NGK 7558 spark plug? The NGK 7558 is a V-Power resistor spark plug built to the ZFR5F specification, designed for reliable ignition in Mercury EFI 4-Stroke outboard engines.

Does the NGK 7558 fit my Mercury outboard? The NGK 7558 fits most Mercury EFI 4-Stroke outboard engines rated from 65 HP to 150 HP.

Is the NGK 7558 the same as an NGK ZFR5F plug? Yes, NGK 7558 is built to the ZFR5F specification, so the two designations refer to the same spark plug.

Does the NGK 7558 replace Mercury part number 33-8M0204728? Yes, the NGK 7558 is a direct equivalent to Mercury 33-8M0204728 and also to Mercury 33-8M0057936.

What thread size does this spark plug use? The NGK 7558 has a 14 mm x 1.25 mm thread size, matching the standard thread on compatible Mercury EFI 4-Stroke cylinder heads.

What is the reach and hex size of the NGK 7558? This plug has a 0.749 inch reach and a 5/8 inch hex size for use with a standard spark plug socket.

Is the NGK 7558 a resistor spark plug? Yes, the NGK 7558 is rated at 5000 Ohm resistance, which helps suppress electrical interference during operation.

What gap is the NGK 7558 set to out of the box? The NGK 7558 ships pre-gapped to 0.32 inches.

What materials are used in the NGK 7558 electrodes? The center electrode core is copper and the ground electrode core is nickel on the NGK 7558.

How much does the NGK 7558 spark plug weigh? The NGK 7558 weighs 0.15 pounds.

What seat type does the NGK 7558 use? The NGK 7558 uses a flat seat design.

How many spark plugs come in an order of the NGK 7558? The NGK 7558 is sold as a single spark plug, so order one per cylinder needing replacement on your Mercury EFI 4-Stroke outboard.