SIERRA SIE18-3900 Piston Ring for Mercury / Mariner 3.5-9.8 HP Outboards, OEM 39-21665A12 Replacement, Standard Size
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SIERRA

SIERRA SIE18-3900 Piston Ring for Mercury / Mariner 3.5-9.8 HP Outboards, OEM 39-21665A12 Replacement, Standard Size

Product Code: SIE18-3900

The SIERRA SIE18-3900 Piston Ring is a standard-size replacement part for Mercury and Mariner outboard engines. It is engineered for precise sealing, helping to maintain optimal engine performance and prevent combustion blow-by.

This piston ring is a direct fit for OEM part number 39-21665A12 and is suitable for both 1-cylinder and 2-cylinder small outboards. It is an excellent choice for boat owners, marine technicians, and repair shops seeking a reliable, OEM-compatible solution.

  • Compatible with Mercury/Mariner 3.5-4.5 HP (1-cylinder) and 7.5-9.8 HP (2-cylinder) outboard engines
  • Direct replacement for OEM part 39-21665A12
  • Standard size for accurate fit and effective sealing
  • Helps restore engine compression and reduce blow-by
  • Sold individually (per each)
  • Designed for easy installation during maintenance or repair

Choose the SIERRA SIE18-3900 Piston Ring to keep your small Mercury or Mariner outboard running smoothly and efficiently.