ORIGINAL: Kweasel
Its easier to make a short reach plug work well in most applications than it is to get people to use the correct plug in a .10 or .15. Why are people so obsessed with glow plugs? Is there that much difference between them? Can anyone listen to an engine and tell what plug is in it? Why does a high end mfg. like Jett recommend cheap K&B plugs. After reading these posts it appears that an engine simply will not run without an OS F plug.
My experimentation with boat engines has shown that there is a difference. Twenty years or so ago, I was using mostly Fox short idle bar plugs for my smaller plane engines, such as a .25 FSR. Worked fine. I had taken a break from boat racing and had forgotten what I used in my 3.5 cc K&B outboard. One day I took the boat to the lake and inadvertantly put a Fox plug in it. No matter what I did, I couldn't get the engine to run right. It would run, but it just wouldn't come up to the speeds that I knew it was capable of. As a last resort, I removed the fox plug and put in a K&B 1S (older engine that needed a short plug). The engine came to life immediately. This is when I came to the conclusion that indeed all plugs are not created equal.
These days I use a variety of plugs, including OS #8 (2 stroke plane engines), OS F (4 strokes), McCoy MC-9 (high nitro boat engines), McCoy MC-59 (low nitro boat engines). I've still got a few Fox and old K&B 1S and 1L plugs, but I don't use them any more.