Champion RV15YC4 Spark Plug, Stock No. 18

The Champion RV15YC4, stock number 18, is a Copper Plus marine plug for inboard and sterndrive gasoline engines. The detail that matters on this one is the seat: it is a taper seat plug, the only one in our Champion marine line, so it seals on a machined cone in the head rather than on a crush gasket.

• Taper seat. Torque it well below what a gasket-seat plug takes. Over-torquing a taper seat plug into an aluminum head is how threads get pulled.
• Gap: 0.039 in (1.0mm).
• 14mm thread, 5/8 in hex, 7/16 in reach.
• Copper core electrode with extended projection for accurate heat range control and longer life.
• SAC-9 semiconductor resistor for EMI and RFI suppression, with TinTac and Ultraseal coated shell for corrosion resistance.
• Interchanges with Mercury 33-896329018 and Johnson/Evinrude 0765904, 0765846, 0772347 and 3854400.

Confirm the plug against your engine manual before fitting.