I have a 1975 135 hp Johnson. Carbs are completely clean, and compression is perfect. However, at idle, she sometimes cooperates and sometimes doesn't. I run the standard johnson outboard oil, $17/gallon, and think this may be to blame.

Do you think if I ran the synthetic stuff...I just read you can buy the synthetic stuff from GI Joes for $20/gallon that it will not foul the plugs. Also, what does it mean to run a hotter plug? Right now, I just have the standard champion plug.

Thanks in advance for any input.

Have you ever tried an NGK sparkplug? I haven't found a 2 stroke (outboard or dirt bike) that didn't run better on an NGK than a Champion.

Ditto on the NGKs! Hard to find hotter plugs in some sizes these days. Scoured the greater Sno Co area a couple of years ago and bought every one I could find for my kicker - should last me a while.

Another thumbs up for the NGK... I have a 1977 140 HP Johnson, same as your 135 except a different exhaust housing. Had constant fouling problems with Champion plugs, then switched to the NGK BUHXW-1 plugs. Runs great now.

Here is a brief description of "hot" and "cold".

I run NGK's in both my outboards as recommended by the manufacturer.

"Spark plugs....We can make this easy or we can make it hard. Let's start with easy. After running for a while normally, stop the bike and take the spark plugs out. They should look a light chocolate brown. If, black and sooty the engine is running too rich in the fuel departement or too cold of spark plug. If black and shiny they are oil fouled. If they are whitish, you are running too lean a fuel mixture and/or wrong ignition timing or too hot of spark plug. When you see this, your engine is about to blow up!!!

Now the harder stuff. A spark plug does not make your engine run hotter or colder. The terms hot or cold refer to the temperature of the tip of the spark plug itself. The plug must keep a temperature of, between 752 and 1652 degrees Fahrenheit. If it gets too hot it can fire off the air/fuel mixture at the wrong time. This can cause detonation and/or pinging which will put a hole in your piston... not good. If it gets too cold it will not burn off the carbon and fuel deposits on it's tip and the plug will foul out (stop working) not good either.

The heat range of a spark plug is controled by the length of the center electrode. A longer one is hotter because it takes longer for the heat to flow through it to the cylinder head. As you might think the cooler plug has a short center electrode."

Edit: One last thing. A hotter plug generally makes for a better idling engine.

GO NGK champion's foul out way to fast.

Great info on the "hot" plugs. I run them on my kicker because of the low rpms. I would hesitate to put them on my main motor because I run that motor hard and don't really want to buy a new one soon. Be careful!!! West Marine in Fife has a good spark plug catalog and it shows how the spark plugs are rated.

The synthetic oil probably won't help you idle any better but it will stop your fouling. No ash residue with the synthetic. It was amazing to see the difference in my old Johnson kicker. I was fouling plugs all the time and now a set will last all season(I would guess that has to be at least 200 hours on my kicker)

Problem for me is now I keep running that old 2-stroke kicker instead of upgrading to a 4-stroke.

Great reply Little Fish, better you than me cause I can't get that across to people so I must not be explaining it in laymans term, and fishingking00, sounds like you should probably let an expereince proffesional handle the situation. I know it'll save you money doin' it yourself, but hate to see anyone get towed in to the boat launch, and could also mean signs of something more. Tight lines.....

Robert

One more little bit... Champion and NGK use different codes for the heat range of the plug. On Champions, the higher the number, the hotter the plug. On NGKs, the higher the number, the colder the plug. Go figure.

Dan

I agree on the NGK Plug. My father is a marine engine mechanic and he and others mehanics have told me that synthetic oil keeps your plugs from fouling faster but that if you use synthetic to stay with it because switching between nosythetic and synthetic can be hard on your engine because the synthetic will cause gaskets and other sealants that hold the engine together to wear faster. I have never tried it or tested it but that is what I am told.
Paul