Spark shoots from boot to Spark plug nut.

[dinikin]

Motor idles fine and does not seem to loose much power.
Just don Seafoam tretment and seems to run better.

Recently I had covers off and notice a spark jump from underneath the rubber boot towards spark plug. Tried crimping the commector and put some dielectric grease on the connector and seemd to be less frequent from about a spark avery second to about one in 10-20 seconds.

What is the deal?
Do I need a new cable?
I treid taking off the boot of the coil and the wire goes inside.
How do I remove that wire from the coil? Is it one piece?

I happens on the lover cylinder, I think #4

 

[bgbass.1]

Re: Spark shoots from boot to Spark plug nut.

you need to change the boot and end you can buy those separate

 

[MercFan]

Re: Spark shoots from boot to Spark plug nut.

Yep, efinitaly replace the rubber boot and the fitting that's inside the boot as bgbass said.
Could also be the spark plug itself. It's easier for the spark to jomp the outside than it is to jump the spark gap.

 

[Texasmark]

Re: Spark shoots from boot to Spark plug nut.

You are experiencing a phenomenon known as "surface creep". To jump a gap (under fixed circumstances) it would take say 10,000 volts, whereas to creep down the surface of a "contaminated" insulator may only take 1,000 sorta thing. It follows the path of least resistance. You have to insure that the higher voltage required to jump the gap IS the path of least resistance.

You either have a problem with what has already been discussed, the surface of your plug is contaminated, or the plugs insulator has (electrically) broken down.

New plugs are cheap.

Mark

 

[Chris1956]

Re: Spark shoots from boot to Spark plug nut.

Spark plugs, wires and distributor caps can have this happen if they get salt water splashed on them. The water dries up and the salt is a conductor. Clean the plug and wire with water and see if that cures it.

 

[dinikin]

Re: Spark shoots from boot to Spark plug nut.

Thanks for ideas and tips.
The spark plug is non adjustable, ther one kinda nipple looking one.
After swapping two plugs problem stayed with the same cable, boot.
If cleaning does not do it, will replace that boot.

Regards,

 

[Chris1956]

Re: Spark shoots from boot to Spark plug nut.

One more thought. Wipe off the spark plug seat and the seat area on the block to assure the plug is well grounded. Check your ground straps, on my inline I has two from the lower cowling to the block.

 

[dinikin]

Re: Spark shoots from boot to Spark plug nut.

What kinda pazzeld me is that: The gap between the boot to spark plug nut is about 1 inch long where as a gap that on the spark plug, Well this is where I am confused. Like I mentioned before spark plug is the kind that does not have an electrode bent over the center but looks more like a Nipple.

Does it shoots to the top of the Cylinder or just across the spark plug.
I do understand that if there was some moisture and some salt on the plug then current would take the pass of least resistance.

And after putting some dielectric grease inside the cap, sparks almost stopped shooting across.

One more thought. Wipe off the spark plug seat and the seat area on the block to assure the plug is well grounded. Check your ground straps, on my inline I has two from the lower cowling to the block.

 

[MikDee]

Re: Spark shoots from boot to Spark plug nut.

Wait, is this a resistor spark plug, or non-resistor? If it's a non-resistor plug sometimes the spark will do that! Be sure to get a Resistor plug then try it, the spark path should be directed into the spark plug internal resistor, give that a try then let me know how you make out.

 

[Chris1956]

Re: Spark shoots from boot to Spark plug nut.

The plug in question should be a gapless non-resistor plug, likely a Champion L76V or a NGK BUHW, or BU8H. The spark is supposed to "walk" from the center electrode to the shell of the spark plug. These plugs were thought to be antifouling, and were used by Merc from the early 70s thru the late nineties. OMC used gapless plugs briefly, but reverted back to conventional plugs.

 

[Texasmark]

Re: Spark shoots from boot to Spark plug nut.

I went back to conventional plugs on my '02 3 cyl 2 stroke and prefer them also.

Mark

 

[inline_1350]

Re: Spark shoots from boot to Spark plug nut.

Electricity ALWAYS finds it's closest point to ground. Obviously to jump the gap is much closer to ground than it is from the boot to the base of the plug. BUT if the plug is bad, it can't find ground and looks somewhere else... Correct answer is bad plug. Ultra extreme gap with the need to burn fuel-oil mixture could create a fouling effect and/or a harder to reach grounding point but even then it's still there at the plug...