I just bought a Mercury 7.5 HP 2-stroke outboard that needed fixing. First thing I did was pull the spark plugs. They are Champion L78V’s. I noticed the electrode design was different from anything I’ve seen before. The center electrode is flat, almost flush with the end of the threads, and the spark jumps from the rim of the plug to the center electrode.
Because there is no way to adjust the gap, it’s a “permanent gap” plug, hence “permagap.” Has anyone tried this on a car engine? Maybe not practical because the plug tip doesn’t extend down into the combustion chamber. I don’t know. I just found it an interesting design and wondered if anyone had tried it in a car engine. The gap does look to be more than is typical in a car engine.