Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

johnbwalsh

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Aug 18, 2011
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The plug was incorrectly fitted and the now threads on head are damaged. I cannot get plug to tighten . Went in with force but blew out after an hour on the water.

Is replacing the head the best option, is this hard, expensive to do ....
 

pvanv

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Apr 20, 2008
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Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

Will a heli-coil work? That would be my first choice. Will cause that plug to run warmer (because it's stainless instead of aluminum), so you may need to go one number cooler for that plug if the plug stays white, instead of coming up a nice tan.
 

johnbwalsh

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Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

Hi Paul

I have been told that maybe a www.timesert.com would be a better choice . Does anybody have experienceof fitting these to a Honda 50HP ?
 

jjohnson120

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Dec 31, 2009
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Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

I've never seen the insert in the link you provided, but I don't see why they wouldn't work. Looks like a good idea to me and I'm going to make a mental note in case this ever happens to me.
 

Sea Rider

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Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

Have placed 2 helicoils on 2 cylinder engines because of repeted extreme overheats that damaged threads, works perfect, didn't need to change plugs at all. It's the least expensive work, probably will need to disassemble head so that metal bits do not enter cylinder while enlarging plug hole with tool to place helicoil insert.

Happy Boating
 

jjohnson120

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Dec 31, 2009
Messages
278
Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

Have placed 2 helicoils on 2 cylinder engines because of repeted extreme overheats that damaged threads, works perfect, didn't need to change plugs at all. It's the least expensive work, probably will need to disasemble head so that metal bits do not enter cylinder while enlarging plug hole with tool to place helicoil insert.

Happy Boating

Very good to know. Seems like a cheaper fix then replacing the head by a whole bunch.
 

Sea Rider

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Sep 20, 2008
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12,345
Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

Placed helicoils on both plugs but with cylinder head disassembled because the head was warped do to excesive heat, the machine shop did a impeccable work and after 5 years still working with no problem whatsoever. Both systems repairs threads, the tech difference is that one is a compact bushing insert, the other one a tough spring coiled bushing insert.

Happy Boating
 

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JB

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45,907
Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

Hi Paul

I have been told that maybe a www.timesert.com would be a better choice . Does anybody have experienceof fitting these to a Honda 50HP ?

Timeserts are superior to helicoils for spark plugs because they are closer to the original heat transfer characteristics and allow you to use the original spark plug model.
 

johnbwalsh

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Aug 18, 2011
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Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

thanks for advice .. have sourced correct time cert kit and will attempt over next few days. Will post part kit details and photos if it works. Mechanic assures me it will last 10 years .. fingers crossed
 

johnbwalsh

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Aug 18, 2011
Messages
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Re: Honda 50HP - Cannot tighten Spark Plug in head. Head plug threads damaged...

The Timecerts worked a treat. Gave the engine two long run outs ...
 
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