"Joe, thanks for the link. I see the heat range of "5" under the specs,
but if "5" is in the middle of the heat range, then their cross reference
to Champion D18Y (549) shows a heat range of "18"…….. not sure
what’s up with that!"

Someone smarter than me needs to chime in on what they think about that plug. I think Champion goes to double digit heat ranges sometimes to space them out further a double digit chart. Not not sure where an 18 would fall into that method. Since its pumping water well I would try the plug it actually calls for which hopefully would help with the heat. I do think its awesome you got it running.

Joe