Folks, adding a post with spark-plug and RPM information for all the Rotax JPS engines in your Vortex.
I’ve added some info for the 4-Tec (150, 200, and 250HP) plugs (DCPR8E) that I wasn’t aware of until recently. There are two versions of this same plug, the NGK 4179, which has a solid, non-removable terminal nut on top, and the 4339, which has a removable terminal nut!All 4-Tec engines should use the 4339, with the terminal tip removed, exposing the threads. Don’t make the mistake of getting the 4179, which has a solid terminal tip which cannot be unscrewed!
The latest plug for the 300 is the NGK KR9E-G, part #93226, which supersedes the earlier KR9C-G, and is a longer-lasting plug. The KR9C-G is physically the same dimensions and heat range, and still OK to run, it just may not last as long as the newer KR9E-G, which was specifically designed by NGK just for the Rotax 300.The 300’s coils are designed to work WITHOUT removing the terminal nut of the plug, this is a significant difference to be aware of! Leave the terminal tip ON when doing plugs on the 300!—Regarding RPM information. Listed here are the normal operating RPM ranges for all the Vortex power packs. You should be within 200 RPM of the recommended RPM at WOT, with best-running engines in good weather (cold) pushing the upper-end of that band if possible.Your RPM performance is a good indicator of your motor’s overall health, as well as the Impeller/Wear-Ring. If your RPM’s are not in this range, you should investigate why, and take any actions necessary to get you there, if you want your boat running best it’s capable of.
