I am not sure your outboard engine issues are spark plug gap related....but it most likely would start easier if the gap was correct.  Two stroke engines can build up an excess of oil when the engine is not warmed up, and started repeatedly, or run at low rpm for extended periods.  The oil can settle out or condense, and then pool in a low spot. (This is a big problem for trials motorcycles and it is why you will hear them rev the engine to clean out the excess fuel/oil before making a high speed run up a steep hill....the excess oil can come up out of the bottom end when the throttle is opened and cause them some problems as the engine chokes on the oil).

When the gap is less than required the spark energy is reduced as the coil doesn't have to make as much energy before the spark jumps the gap.  This most likely would cause running problems under full throttle use.  The carbon build up is not related to the spark energy - but to the heat of the combustion process that keeps the plug insulator hot. Rich mixtures, lots of cold starts, lots of engine idling....all those things can make the plugs black.....especially in a 2 stroke.  Be sure to use "outboard" rated oil, as some of the general purpose 2 stroke oils just don't burn cleanly in a cool running outboard motor.

The Savage plug should be between 0.031" - 0.035".  The tailpipe will always be black and sooty - the ethanol laced fuel just seems to come out the exhaust pipe that way....even in a fuel injected motor.

Raydawg, you might be running to much yamalube,but if I could  choose between cleaning or changing a spark plug or turning the motor into an anchor... I' d clean the plugs ,and reuse them.

From what I've seen of oil injection on bikes, it's much worse than premix when running at low speeds.  You speed up and put out a huge cloud of smoke until it burns off.

I've always thought that a shorter spark is a hotter spark. The electrical system puts out whatever amount of voltage regardless of the plug gap. A short spark has more energy per unit of length. Am I correct?

The spark does not keep the electrodes or the insulator clean - the combustion heat is retained in the porcelain insulator, and the longer the insulator the more heat is retained....that is what the "heat range" of the plug is established.


That's good information.. Thanks

From NGK:

Spark plug gap

Always check that the spark plug gap is compatible with the engine manufacturers specification. A gap that is too small means that the spark duration will be very quick and the spark will be thin and weak. The consequences of this may be bad starting and high exhaust emission levels. This will result in an increase in fuel consumption. If the gap is set too large, the ignition system will not be able to cope with the demands and a misfire situation will occur. Some wide gap spark plugs have a longer ground electrode to accommodate a wide gap setting. These must be used where specified, as opening up a standard plug to a wider gap setting may result in the electrodes not running parallel to each other. This could result in abnormal and premature electrode wear.

The re-gapping of fine wire spark plugs that have very small diameter platinum or iridium alloy electrodes is not recommended due to the risk of damaging the electrodes. Virtually all NGK spark plugs are set to the correct gap for the catalogue applications at the point of manufacture.