Home › Forum › Ask A Member › 15hp ignition conversion plug change › Re: 15hp ignition conversion plug change
June 2, 2017 at 11:40 pm
#58846
When you upgrade to CD ignition, the NGK plug would be the BR9HS-10. The -10 is a plug made to have .040 gap rather than the same plug number without the -10,which is to be gapped at .030. Note that NGK heat ranges are hotter with a lower number after the BR. I’ve also found that some vendor websites disagree with each other on which heat range to use.
Below is one chart on which plug should go in the 9.9/15 Johnsons – note in 1980, the ignition was made more robust and the -10 plugs spec’d for the .040 gap – see below: