Re: NGK's vs Champions
Some of the NGKs are not a direct cross for certain Champions. They may be off a tiny bit or they may actually be off enough to cause a problem in some circumstances.
If you have an OMC that's set up properly - can reach max rpms with an average load, the ignition is correct, the fuel delivery is correct, it's running on fresh 87 octane and the motor is stock - it'll probably be OK with NGKs or Autolites or whatever as long as the heat range is close to being correct. Some OMCs are more forgiving in that department, some aren't.
If you have an OMC motor that's running a tad on the rich side or backed off on the timing a little, it may actually benifit from a bit hotter spark. Again, regardless of who makes the plug.
If your OMC is lugging or running old gas / wrong octane or wrong timing or anything that contributes to a higher combustion temp, you're asking for trouble by adding to that (already) higher than normal combustion temp.
Think of the opposite situation - Mercs and Yamahas, generally speaking, run better with NGKs because that's what they're calibrated for as stock motors from the factory. Again, generally speaking if a given Champ is a little cooler than the NGK that's supposed to be in there the motor will foul the Champ pretty easy. That's why you usually hear a Merc or Yamaha guy bad mouth Champion.
I'm not saying we've never run NGKs in OMC motors, we have. Especially race motors, even OMCs. But we dump a lot of fuel. A lot. We've even switched back & forth from NGK to Champ and vise versa depending on what the weather did.
But overall you'll find that correctly running OMCs run better with Champs and correctly running Mercs and Yamahas run better with NGKs. Basically if you run too cold a plug it may foul out. If you run too hot a plug it'll burn the electrode, perhaps the piston.
I've had guys insist on running NGKs in an OMC even after they burn a piston. We simply richen up the mid range a little and a bit on top. No more problem.
