Lets talk spark plug wires and boots!

[YammyMan]

I am really having some confusion. Cant wait to hear what you veteran Yamaha folks have to say about this. I have a 1999 c60. I have the original wires, boot and coils on the motor. I decided today to take them apart and inspect them. This is the type where the wire screws into the boot and into the coil. I pulled out my multi meter and ohm'd my wire. It was good. Continuity. So I decided to ohm out the boot as well. To my surprise from the screw to the part that clips onto the top of the spark plug, open. HMMM. So I tear apart number number 2. Same senario. Number three, yup you guess it the boot is open. So can someone tell me how it is possible to have an open boot with no continuity and the motor still run. Is there some sort of device in the boot which closes when voltage is applied? Or are my boots going bad? The motor runs with no problem. Also does anyone have a part number for spark plug wire that I can use to replace the old wires? The only part number I have found is for the boot 6G1-82370-20-00. Look foward to hear what you guys have to say about this one!

[99yam40]

My guess is that you did not have the meter set to the proper setting to get the reading.
Might check in service manual what the boots ohm spec is to make sure you set the meter to a setting that can read that

[YammyMan]

Yeah that would have been my first thought to. But Im using a fluke mulit meter on auto range. So it should have ranged to that ohmic range. I will go to the manual and see what it says. Didnt know it gave an ohm reading for the boot. Thanks for the reply.

[YammyMan]

The only reference in my manual to the spark plug cap is screw it on. It gives ohmic reading s for the coil but not the spark plug cap. Ugg

[YammyMan]

I think i attached a document. Check it out. This is what my manual says.

[99yam40]

Sorry, I thought if they were replaceable then they would give a spec

My C40TLRX manual shows the screw on type outside US as 4.0K ohm - 6.0K ohms

[rodbolt17]

ok lets talk.

if the caps are orange then you can test them.
if they are black with spring clips you dont.
if you removed the secondary wire from the coil you destroyed it.
why are you checking it?
did you note there are two different wires shown in your manual?

[YammyMan]

Ok. I have black boots which are the screw on type. And my coils are also the screw on type. They are all original. My motor is a 1999 and there is actually a date on my wire that says 98'. I was thinking that maybe my slighty rough idle could be from dropped voltage from a worn wire. But man was I surprised when I couldn't get an ohm reading from the boot(touch the screw with one lead from the multimeter, and touching the other lead to the inside of the spark plug cap). I am still baffled. But even more baffled as what type of wire I can replace it with. Is it coppered tin alloy 18 gauge 7mm wire? I have not found this info anywhere. Just alot of questions about this set up. Or does yamaha want me to replace it as a boot wire combo from them?

[rodbolt17]

make sure your meter leads are touching the mettalic parts inside the boot.
sometimes I use a screwdriver as an aide.
if you removed the plug wire from the coil odds are high you destroyed it.
thats why the coil and wire is sold as an assy.

not all yamaha coils have removable wires.
easy way to tell is look at the parts catalog,if the wire is a seperate part number its a removable design.

its also why I use a Kv tester.
eliminates or confirms secondary fireing voltage almost instantly.

[YammyMan]

Trimming Spark Plug Wires from the coils for a 2 stroke Arctic Cat ignition - YouTube Check out this link on youtube. My coil, wire and boot operate the same as this.

[Pterodactyl]

Hi

Some ignition HT circuits have a ' air gap ' on purpose, I've only seen this in automotive coils, (Nissans are common) never on boat engine plug caps. I dunno if yours is supposed to. This airgap is to force a higher voltage to be produced at the plug. 2 reasons,
1 to blow crud from the gap
2 to provide a more agressive and reliable combustion.
quite a good idea but eliminates the ability to test ht secondary resistance.

I've found the NGK jetski boots quite successfull. I've had excellent success with the blue 5k ohmm type.

The reason for this resistor spark plug cap or lead is two fold
1 to provide some radio suppression or engine speed clicking over the radio and vhf.
2 to make the ignition system last longer although the manufacturer may be a little uncomfotable agreeing.

[YammyMan]

Great info. Thanks for you input!

[Pterodactyl]

Sorry, I forgot one of your questions

HT cable
7 mm refers to the thickness of the insulation, the thicker the better to a point.
The conductor or the wire up the middle that carries the energy, on a boat I'd suggest tinned copper as copper is a great conductor and the tinning process slows up the rate of corrosion.
Aluminmium alloys are much less conductive but alot cheaper to produce.
Aluminium is also less maliable or resistant to flexing than copper.

Flexibility , ability to shed water , resistant to oil and petrol and salt water corrosion resistant are some things to consider.
On boats I thread the ht cables inside a thin wall tube of pvc to slow up the ingress of water and petroleums. I also use a little automotive silicone around the outside at the ends to keep the water out and to provide a little more mechanical stability.

so when removing spark plug caps be gentle

worst thing ever is to wind over with the key on and spark plug caps floating not connected.
Regards Don

[YammyMan]

So do you think this type of wire would be a good choice for replacment wire?

7mm Black Spark Plug Wire Copper Core | eBay