Threads Stripped Out, Need To Fix...


Old 04-12-09, 08:51 AM
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Join Date: Jul 2006
Location: Virginia Beach
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Threads Stripped Out, Need To Fix...

Not sure which forum this would be best in (boat/auto) but I thought auto wrench-turners over here might be more experienced with this predicament...

My boat which has twin 496HO Mercruiser engines comes each with a decorative manufacturer plastic engine cover. Each mounts on top of the engine intake manifold via three fairly long bolts or screws with brass spacers providing space between it and the motor. Well one of them came loose and sort of vibrated out causing it to round out the threads on the intake manifold end of two of the three mount screws. Well I want to obviously fix this, but I'm not sure if I should use a tap set which may make it a bigger hole requiring a bigger bolt/screw? Or if I should find a helicoil kit and go that route?

If I use the helicoil method, don't I have to also drill out the hole bigger to take the helicoil? I've actually never had to do either myself before. Have watched others, but never really piad attention to the details........Thoughts?
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Old 04-12-09, 09:21 AM
Gunguy45's Avatar
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If this is a non-high torque situation, which it sounds might try one of the epoxy thread restorer kits first. I've used them in some situations before, and if you have at least some thread left in the hole, they work pretty well. Cleaning any grease or oil out of the holes is vital.

Something like this

Otherwise, the helicoil would prob be your best bet. And yes, you need to drill and tap the hole to a larger size, then install the insert.
Old 04-12-09, 10:07 AM
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Bring the bolt with you to the store.....They come in specific sized "KITS"....Follow the directions on the package...and your done.

Also pick up a Tube or jar, or can of Anti sieze Compound.....I do realize it is a low torque application, but Helicoils can "Back Out" under stress.
Old 01-04-10, 04:16 PM
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Join Date: Jul 2006
Location: Virginia Beach
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Haven't gotten around to it actually. One of those crazy busy summers, but now thinking back on spring projects coming up.

This actually has to withstand quite a bit of vibration hence the problem in the first place. So drilling out the hole is so the helicoil can be screwed into the block right? Then the screw/bolt in turn fits/screws in to the helicoil? Sounds pretty straight forward.
Old 01-04-10, 04:23 PM
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I would do as Unk said and use something like Locktite to keep vibration from doing it again.
Old 01-04-10, 06:16 PM
Join Date: Nov 2006
Location: Jersey
Posts: 526
An alternative to heli-coil is Time Cert.
Time Certs are similar to Heli-coil but easier and use and holds up great. (not sure of the spelling)
I used this on my rocker studs and it's still holding after 160,000 miles later. (high torque)

I have used Liquid Steel on my lawn tractor Starter mount studs but they kept pulling out. (high torque)
Old 01-13-10, 04:43 AM
Join Date: Aug 2009
Location: Ohio
Posts: 11
I have used the helicoils and was very impressed. I dont think that you would have to drill out as much as if you were going up to next size bolt (like from 3/8 to 7/16). Kit is expensive but the finished result is, in my opinion, as good as new.

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