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I should get a spark out of you. (2 cycle motors)
In response to field requests for alternate spark plugs, where standard replacement spark
plugs are not available or unusual operating conditions exist, such as cold fouling or
where pre-ignition and/or piston burning is a problem, the following information is
offered.
To determine if a substitute spark plug is to be used, the spark plugs should be removed
from the engine and examined for general appearance. Determination should be made that all
possible causes of spark plug fouling have been eliminated. Listed below are typical
conditions for spark plugs that are running too hot, normal or too cold and possible
causes for these conditions other than an incorrect spark plug.
Note: These
colors are to be checked on a motor that has fully warmed up, and not idled for more than
a minute or so.
Standard Battery and Magneto Ignition
1. Spark Plugs Too Hot: Plugs will be white or light gray in color on the spark plug
insulator. The spark plug insulators may have a blistered appearance and electrodes may
erode prematurely and exhibit a blue color. Possible causes, other than incorrect spark
plug, could be:
A. Carburetion too lean (main jet)
B. Ignition timing over advanced
C. Sticking piston rings
D. Wide open throttle R. P. M. too low (lugging engine)
E. Reduced water flow (due to restricted water passages, bad water
pump)
2. Normal Spark Plugs: Plugs will have a light tan color on the insulator with few
deposits present. Electrodes will not be burned or eroded. (a slightly oily appearance is
normal if the engine was idling for more than a few minutes before plug removal
3. Spark Plugs Too Cold: Plugs will have a wet black appearance. Possible causes other
than incorrect spark plugs could be:
A. Prolonged trolling operation
B. Carburetor idle adjustment too rich
C. Improper fuel/oil ratio (excessive oil or poor mixing)
D. Worn or defective breaker points
E. Blocked passages or blocked check valves in the fuel recycling
system
F. Thermostat stuck open.
G. Cooling passage restrictors missing.
H. Weak spark, bad or shorted to ground plug wires or poor ground at
coil.
Champion, AC, Autolite, and Bosch spark plug manufacturers have spent large wads of money
to test and manufacture the correct plug for each motor, and the chance that they are
wrong is pretty slim. If your having problems with plugs, try a different manufacturer,
first. Check on a plug update or plug alternative offered. (contact the dealer or marine
parts supplier) Then, If none of the conditions listed above exist, hotter
sparkplugs should be used where cold fouling is the problem. Colder spark plugs should be
used if pre-ignition or piston burning is a problem.
(See Champion or NGKSpark plug
charts on this web site) |
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