Suppose the insulator firing nose contains either wet or dry dark color deposits. NGK Outboard Motor Spark Plug Guide Table of Contents Outboard Motor Brand NGK spark plugs are original equipment on many outboard motors and are excellent replacements for everyday engine maintenance. Champion L86C Marine Spark Plug Champion marine spark plugs are quality OEM replacements. By this method as the powerplant gains engine hours the gap widens into its spec, as opposed to an initially wide gap that begins to goes out of speck with the first turn of the key. 3/4" Reach 5/8" Hex R7434-8 4892 162 DV Iridium R7434-9 4658 162 DV ISO, Low Angle Ground Electrode R7434-10 4894 162 DV Gasket, Solid Resistor 3/4" Reach 5/8" Hex R7433-8 4889 161 DU Weak spark could also be the culprit. Finally, the fuel octane might be too low for the engine, or the gas stale. In general, if an engine logs lots of hours trolling, and the plugs are black, it's a safe bet the plug isn't hot enough. But dont worry: Moving forward doesnt mean were leaving our heritage and quality standards behind.Our new company name Niterra expresses the Groups desire to be a company that not only contributes to a sustainable society, but also one that makes the earth shine. Replacing Your Marine Spark Plugs in 11 Easy Steps. MarineEngine.com does not offer troubleshooting assistance or repair advice by email or by telephone.