Spark plug hole was rethreaded, need help??

[Incaboater]

I bought the boat and never knew this but the middle cylinder spark plug hole was rethreaded. I guess the previous owner had stripped it and needed to redrill-rethread it to put a new spark plug in. I pulled out the spark plug and the threaded area of the spark plug had a sleave screwed onto it with threads that fit the new larger hole. The only problem is that the sleave doesn't come off of the spark plug so I can't use it on the new spark plug, what do I do. Also small amounts of fuel is leaking from that spark plug hole, how do I stop that? Is there any seal I can put on the theads to stop the small leak?

 

[clemsonfor]

Re: Spark plug hole was rethreaded, need help??

That's a heli coil, either buy more of that size and use them and see if it leaks or buy a new cyl head cover, you can probably get one on ebay or a outboard salvage place for not much money compared to the head ach something like that may cause.

-Nate

 

[Incaboater]

Re: Spark plug hole was rethreaded, need help??

Wow, thanks for the quick response. Where might I get one of these? Any local hardware stores have one, or is it a specialty thing?

Thanks again,

 

[kynolan2183]

Re: Spark plug hole was rethreaded, need help??

Get the heli coil at the auto parts house...

 

[R.Johnson]

Re: Spark plug hole was rethreaded, need help??

See if you can find a machine shop that can install what is called a Keen-Sert. This has a sealing surface, and is locked in the threaded hole with metal stake's to keep it from backing out with the plug. You can't just screw in a heli-coil, and call it quits. If screwed in to deep, it can act as a glow plug such as in a model engine, and cause pre-ignition. I would replace the head before using one of those. To me, it is a very poor repair.

 

[F_R]

Re: Spark plug hole was rethreaded, need help??

A Heli-Coil looks like a spring. You say yours won't come off the plug, so I doubt you have a Heli-coil. But if you do, they need a special tool to install, and cannot re-used because they have an installation tang which has to be broken off after it is in the hole.

Run it by an automotive machine shop for good advice on whatever you have. That's what they do there.

 

[kenmyfam]

Re: Spark plug hole was rethreaded, need help??

Replacing the helicoil is not out of the question. Measure the one that comes out with the plug so that you dont go "too long" with the replacement coil. Either apply a high temperature thread sealant to the new one and / or keep a spare coil on your spare plugs that you can put in in case it happens and you need to replace that plug out on the water.
I have one helicoil in my V4 Johnson. It has not come out with the plug yet but when and if it does I am prepared by having one of my spare plugs with the helicoil in place and ready.
Good Luck.

 

[DHPMARINE]

Re: Spark plug hole was rethreaded, need help??

At the auto parts store look at K D sparkplug inserts.If that is what you have,they are easy to install since your plug hole is already tapped for it.

DHP

 

[bigtwin]

Re: Spark plug hole was rethreaded, need help??

DHP is right on the money the K D inserts are the best. I have two of them installed on my 25 hp. for several seasons and havn't had a problem with them yet, however they run a bit long, the plugs for my engine have a 1/2" reach, I found the 1/2" inserts were too long, and had to use 7/16" inserts, I know NAPA sells both the K D kit, and replacement inserts under there own name.

Good Luck!!!!

 

[kenmyfam]

Re: Spark plug hole was rethreaded, need help??

Any good tool and die shop supply store will have all the helicoil variations you need and at a lower price than the auto stores especially if you give them a local tool and die or machine shop name when you buy them.

 

[Chris1956]

Re: Spark plug hole was rethreaded, need help??

Incaboater. As you may know, a Helicoil is not a solid insert. It is sort of a spring. If you have a solid insert stuck on the plug, buy some MarineTex, clean up the insert and threads with some acetone, mix up a bit of the MarineTex, smear it on the insert's threads and screw the plug and insert into the motor. When the MarineTex hardens you should be able to remove the plug, and the insert will stay put.

 

[Incaboater]

Re: Spark plug hole was rethreaded, need help??

Thanks for all the info guys. Ya this is definitely no helicoil, its just looks like a very thin tube that has threads on the inside and out. The outside threads are to go into the rethreaded cylinder head and the inside thread of the sleave is for the spark plug to screw into. Thanks for the help. So you say marine tex. Will this permanently bind that insert/sleave into the cylinder head/?

 

[clemsonfor]

Re: Spark plug hole was rethreaded, need help??

should!

 

[DHPMARINE]

Re: Spark plug hole was rethreaded, need help??

Marine -Tex is a great product.I've done many things wih it.

But if you have a KD insert,Loctite is needed.

DHP