Sierra Spark Plug Boot Fitment to Champion Plugs

[JohnnyGuy]

Hi all, I purchased a 10pack of Sierra Spark Plug Boots (18-5750-9) after running some new plug wires only to find out after I'd had them installed that they do not fit over the recommended J6C plugs that are called for.
Has anyone else noticed a fitment issue with these boots onto Champion plugs?
Checked a second bag of the same Sierra part and its the same thing, they don't fit over the champion plugs... They're supposed to be a direct replacement for the OEM boots (581027) which are used on MANY JohnnyRude motors that call for the J6C plugs.
I even contacted Sierra and was basically were told that if they don't fit, I should purchase the OEM boots... :\

 

[racerone]

Any pictures of the old boots and these sierra replacements.------Seems strange that a common part like that is giving you problems !

 

[JohnnyGuy]

Any pictures of the old boots and these sierra replacements.------Seems strange that a common part like that is giving you problems !

I've attached a Photo and below is the correspondence between the shop I purchased the boots from and Sierra.

Shop:
I sold a customer part # 18-5750. It is to small to fit over the spark plug. The OEM part number is 581027. Do you think it is packaged wrong or have you had other fitment issues?
Please let me know

Sierra:
There is a chance that this is packaged wrong, but I would doubt it as we really only have two different options for spark plug boots (the 18-5750 or 18-5752 which is a different style of terminal). We have also not had any reports of fitment issues, so it could also just be that these are not the correct one for the type of spark plugs used on the customers application. I do know that these do fit very tight when new, so it may just require a little more force to initially install it. Sorry I could not provide an exact answer.

My Response which the shop forwarded to Sierra:
Hey, I had another look at this tonight. They definitely don't fit properly.
I have taken some screen shots from the evinrude websites.
For instance a 1975 Evinrude 6hp calls for boot part number 581027.
1965-1976 6hp's call for J6C champion plugs.
As you can see, the Sierra boots I have 18-5750 are supposed to be the equivalent of 581027, but you can see from the photos that they don't fit the plug properly. They are way too tight to go over the porcelain of the plug properly.
I took some measurements of the boot with my calipers.
ID of the wire end is just shy of 7mm
ID of the plug end is just shy of 9mm
OD of the porcelain on the plug is a little over 12mm.

Sierra Reply:
I went out and measured an approved sample of that spark plug boot and I am getting the same measurements as the customer, so this is not a case of a mispack. The only other thing that could be is an incorrect interchange on our end. I will pass the information on to our product team to have them investigate it further, but for the time being I would recommend that the customer go with an OEM version of the boot.

 

[poconojoe]

When you try to put the boot on the plug, do you get the clicking feeling snapping sound that would indicate it's making the [electrical] connection? Or are you just worried that the rubber part of the boot kind of looks too short?

If it's making [electrical], you should be good.

You could try a dab of dielectric grease to get the boot to slip on better, help waterproof it and to get a better electrical connection

 

[oldboat1]

any chance a spark plug connector (spring and spike) is in there crosswise, blocking insertion?

 

[JohnnyGuy]

When you try to put the boot on the plug, do you get the clicking feeling snapping sound that would indicate it's making the [electrical] connection? Or are you just worried that the rubber part of the boot kind of looks too short?

If it's making [electrical], you should be good.

You could try a dab of dielectric grease to get the boot to slip on better, help waterproof it and to get a better electrical connection

The inside diameter of the boot is too tight for the plug. I have FORCED a boot into the plug but it's MUCH tighter than what I would consider normal. When you remove the boot from the plug you get one heck of a loud *POP* and it's not easy to do.

The photo I attached is where the I.D. of the boot stops at the top of the porcelain. The stud of the plug doesn't reach far enough into the boot to connect with the spring as photographed.

 

[JohnnyGuy]

any chance a spark plug connector (spring and spike) is in there crosswise, blocking insertion?

No sir. That's not the problem.
I liken the situation to trying to force a 1-1/4" diameter metal rod into a 1" diameter rubber housing... Yeah you can do it with enough coaxing but it's really not meant to be (IMO anyways).

 

[oldboat1]

think it's closer to fitting than you describe, though. Try some dishwashing liquid on the plug.

 

[JohnnyGuy]

think it's closer to fitting than you describe, though. Try some dishwashing liquid on the plug.

I thought maybe it was just me but the staff at the parts store where I purchased them agreed that it's like the boots are the wrong size for the plug.
I'm going to my local Evinrude dealer tomorrow and will be picking up some OEM boots as I KNOW they fit properly.
I'll measure the OEM to compare to the Sierra measurements for schitz-n-giggles.

 

[oldboat1]

right approach, imo. but a curiosity.

 

[poconojoe]

I was, again, going to suggest using dielectric grease to coax them on, but at this point, get the OEM boots and be done with it.

To me, there are some repairs where I will only use OEM and spark plug wires are not in that category, at least I didn't think so!

Sometimes stupid things like this can be such a pain.

 

[F_R]

Just face it, the Sierra boots are wrong. They have made a change along the line somewhere. Sierra boots used to be blue and fit ok, but some people complained about the non-authentic color. So obviously there has been a change. I hope they will recall and fix the problem.

Kind of reminds me of the Sierra coils that don't fit. It's been forever and they still are showing up. C'mon Sierra, your reputation is on the line.

 

[F_R]

Hm-m-m--m, could it be that they are sending boots that are intended to fit the coil ends of the wires on newer motors????? (0580339 fits coil end)

 

[F_R]

Like this

 

[JohnnyGuy]

Well, I picked up the OEM 581027 boots today.
Photo attached shows Sierra boots on top, OEM on bottom.
ID of the OEM boots at the plug end is just over 9.5mm and it fits snugly (& what I would consider properly) around the plug. The bigger diameter and what seems to be somewhat softer rubber makes all the difference.

 

[poconojoe]

Well, I picked up the OEM 581027 boots today.
Photo attached shows Sierra boots on top, OEM on bottom.
ID of the OEM boots at the plug end is just over 9.5mm and it fits snugly (& what I would consider properly) around the plug. The bigger diameter and what seems to be somewhat softer rubber makes all the difference.

View attachment 339108

Excellent!
Who knew spark plug boots would be such a hassle....
Add them to the "use only OEM" list!

 

[JohnnyGuy]

Excellent!
Who knew spark plug boots would be such a hassle....
Add them to the "use only OEM" list!

Right?!
I thought I was going crazy with the Sierra boots!

 

[poconojoe]

Right?!
I thought I was going crazy with the Sierra boots!

I think I used them on my 4.3 Mercruiser a couple of years ago. The ones I used are blue too. I didn't have any problems.
They must have changed something in the production. Probably trying to save money.... or rather increase profit.