NGK Spark Plug – BPR6EFS 3523

The NGK BPR6EFS is a resistor, projected-tip spark plug used in marine gasoline engines that specifically call for this plug style. The important specs are the BPR6EFS plug code, resistor design, projected firing tip, gasket-style seat, and correct reach/heat range match. Spark plug reach and seat type must match the cylinder head; using the wrong seat or reach can cause sealing problems, pre-ignition, thread damage, or internal interference.

Key Features

• NGK part number: BPR6EFS
• B = 14 mm thread size
• P = projected insulator / projected tip
• R = resistor plug
• 6 = NGK heat range 6
• E = 19 mm / 3/4 in reach
• F = tapered/compact plug style family designation
• S = standard copper-core electrode style
• Commonly used where a projected-tip resistor plug is specified

Engine Compatibility

Fits engines that specifically call for NGK BPR6EFS. This plug is commonly used in select GM-based marine engine applications, including certain MerCruiser, Volvo Penta, and other marine gasoline engines when listed in the engine service specification.

Serial Number Fitment Notice

Confirm by engine model, serial number, ignition system, and service manual. Do not substitute based on thread size alone. Reach, seat style, heat range, and plug gap all matter.

When This Part Needs Replacement

Replace during tune-ups, hard-start diagnosis, rough idle, misfire troubleshooting, fouling, poor acceleration, or after long service intervals.

Installation Notes

Set the spark plug gap to the engine manufacturer’s specification before installation. Install into clean threads and torque to the correct spec for the cylinder head and plug seat type. Do not mix tapered-seat and gasket-seat plugs unless the engine manual specifically calls for that style.

Alternate/Superseded Part Numbers

• NGK BPR6EFS

Parts Desk Insight

The easy mistake is treating BPR6EFS, BPR6ES, and BPR6FS like close substitutes. They are not automatically interchangeable. The letters define reach, tip projection, resistor construction, and plug body style, so the safest match is always the exact plug code listed for the engine.

Shipping: Ships same or next day for fast Canada wide shipping.