Osculati 47.558.55 – NGK BU8H Marine Spark Plug
The NGK BU8H (Osculati 47.558.55) is a robust, non-resistor-type spark plug tailored for 2-stroke marine engines with short plug seating and high fuel loads. Its wide 21 mm hex makes it suitable for engines with large plug wells. The hot heat range (8) helps reduce carbon build-up in low-speed operation, such as trolling or idling. It’s ideal for older or high-displacement 2-stroke outboards where strong, uninterrupted ignition is critical.
Key Features:
- Non-resistor type for maximum spark energy transfer
- Hot heat range reduces plug fouling at low RPM
- Wide 21 mm hex for compatibility with deep plug wells
- Short 9.5 mm thread reach for legacy engine designs
- Nickel alloy construction for marine corrosion resistance
Technical Specifications:
| Attribute | Value |
|---|---|
| Model | NGK BU8H |
| Osculati Code | 47.558.55 |
| Thread Diameter | M14 × 1.25 mm |
| Reach | 9.5 mm |
| Hex Size | 21 mm |
| Heat Range | 8 (hot) |
| Gap | Factory-set (typically 0.7–0.8 mm) |
| Resistor | No |
Manufacturer Compatibility:
- Yamaha
- Mercury
- Mariner
- Suzuki
- Tohatsu
- Selva
- Honda
Cross Reference:
| Brand | Model |
|---|---|
| NGK | BU8H |
| Champion | L6VC |
The NGK BU8H is a trusted choice for technicians servicing classic and heavy-duty 2-stroke outboards. Its simple, rugged design and non-resistor core deliver a powerful spark with minimal voltage drop — especially valuable in older or high-compression engines with analog ignition systems.
