Plugs & smell

1987 Johnson 70hp – This engine had NGK-BR9HS-10-00 installed when I bought it a couple of months ago, they are gapped to .040 and all three have a toasty brown look to them and all seems well. Of course they are not the recommended plugs for this engine. The owner’s manual recommends Champion QL77JC4 gapped to .040 or for sustained high speed operation (probably more like how I use my main engine) Champion QL78V permanent gap plugs. It also calls out L77JC4 & L78V as alternates (I assume these are the same but non-suppressor types).<br /><br />The engine starts and runs fine both high and low speed but it smells bad. I don’t know how to describe it, it’s just foul. I’ve been around 2 stroke engines as long as I can remember and I haven’t smelled one quite like this. Tried a different oil but the smell didn’t change. Could it be the plugs? The obvious answer is to try one or both of the Champions and see (or smell) the difference but I was just wondering if anyone else has experienced something like this.

Re: Plugs & smell

The only source for varying odors is the fuel or the oil. Fuel doesn't vary much. Different brand and type oils can produce different odors in the exhaust. Try a fresh tank of fuel and a name brand oil. Are you sure it is the exhaust your smelling, and not a wire on a manifold, new paint on something hot, or a fresh coating of oil on the motor?<br />Good luck

Re: Plugs & smell

Thanks. I’m kind of grasping at straws here. The smell is definitely the exhaust, nothing is burning on the engine itself and the temperature seems fine. Smell goes away when the engine is off. I’ve tried OMC and Supertech oils, doesn’t seem to matter but maybe I got some sort of blend going now. I’ll try a fresh tank of something else.