See full version: Silver core plug on top of the power head
To increase the plug gap using a simple gap tool, place the end of the ground electrode in the hole and carefully push down on the end of tool. Reeves warns that a too-wide gap can create the situation where the spark fires sideways to the edge of the plug. While the spark still occurs, it can retard the timing by as much as two degrees.
The disadvantage is this will concentrate the spark on one side of the center electrode. With a traditional copper-core plug, the center electrode will wear much more quickly and the gap will increase. This is a trick that is perhaps best left to short-duration race engines. Another option for power-adder applications is to choose a surface-gap plug. Autolite offers the X-series of plugs that has slots cut in the end of the plug, creating sharp edges that make it easier for the spark to jump the gap.
Dispelling The Spark Plug Myths
Reeves makes an excellent point. “I wouldn’t want someone to run a projected tip, standard automotive plug in a 1,200 horsepower, 32 psi LS engine because it’s street-driven.” [links]
Let’s look at some facts that support why fine-wire plugs are a good choice for a performance engine. more
The change to the hotter plugs improved the idle quality only slightly by reducing the unburned hydrocarbon (HC) count along with a slight improvement in CO2 which is an indicator of combustion efficiency. So thecombination of increasing the heat range, and the platinum center electrode contributed to making the engine idle better, cleaner, and more efficiently. here
Smear the mating surfaces of both plug and hole with gasket sealant. [links]
Access is the next problem. You may have to disconnect the carburettor . more
The edges of a cup plug may project far enough for you to pull it out with two pairs of pliers. Grip the edges firmly and pull with an even amount of force on both pairs of pliers. Do not lever against the block — you may damage the plug seating. [links]
For a cup-type plug, find a socket which fits snugly inside the cup. Hold the cup absolutely square and flat against the hole, and drive it home by tapping the socket with a soft-faced hammer.
The plugs are set in various places around the engine block and cylinder head .
There are two common types of core plug, the cap type and the domed-disc type, which are inserted in different ways. here
Does this help to identify my motor?
I can't find a s/n on this outboard I just got. I checked the silver core plug on top of powerhead, or I assume that's what it is, it has a big M, then under that it says J3339923.
Re: silver core plug on top of powerhead
3. Gapping fine-wire spark plugs here
Torque is crucial in the ability of the plug to dissipate heat and perform properly. Always follow the manufacturer recommended torque specification. An under-torqued spark plug can lead to excessive vibration and improper heat dissipation, causing spark plug and/or engine damage. Over torquing may cause any of the following: thread damage/breakage, compromised internal seals leading to gas leakage, metal shell stretch leading to poor heat dissipation and pre-ignition. [links]
NGK spark plugs feature trivalent plating. This silver or chrome-colored finish on the threads is designed to provide corrosion resistance against moisture and chemicals. The coating also acts as a release agent during spark plug removal. NGK spark plugs are installed at the factory dry, without lubrication or anti-seize.
While most NGK spark plugs are pre-gapped, there are occasions when the gap requires adjustment. Care must be taken to avoid bending or breaking off the fine-wire electrodes. NGK recommends a round wire-style or pin gauge gap tool to measure the gap. If the gap must be adjusted, use a tool that only moves the ground electrode and does not pry between or against the electrodes. NGK also recommends adjusting the gap no more than +/- 0.008” from the factory preset gap. [links]
Corona stain is a light brown or tan discoloration on the outside of the ceramic insulator above the metal shell/hex. Corona stain is created by the high voltage traveling thru the plug that attracts the dirt or oil particles surrounding the exposed ceramic insulator between the wire/coil boot and spark plug metal shell. Corona stain is completely normal and should not be mistaken for exhaust gas blow-by or a broken seal inside the spark plug. here