Insufficient threads on keel bolt. Double nut?

[Swift Drift]

While torquing my keel bolts to spec I had one nut that would continue to spin without reaching the appropriate torque.
Upon further investigation I found the threads towards the bottom of the bilge are not substantial enough for the nut to grab. It will start to grab and then jump the threads. Here is a pic of the length of the keel bolt:


My plan of action is to add another nut which will be able to grab the upper threads and torque nicely. Effectively the bottom (1st) nut would act as a spacer/washer allowing the upper (2nd) nut to access quality threads.

Can anyone find fault in my reasoning?

[RaymondR]

I'd put a couple of more washers under the lowest nut to ensure that you have good threads over the full depth of the top nut.

[NYSail]

I would possibly figure out if you could remove and replace the threaded rod that goes into keel. Wonder what caused it and what it looks like further down... what make boat? Is it leaking?

Greg

[Swift Drift]

Good idea with a couple of more washers however I think the height of 1 nut will get the 2nd nut onto good threads no problem.

My understanding is the rod is a "J" shape encased into the keel and hence would be a huge project to remove. Why remove/replace if I can attain torque specs? The keel bolt is not leaking. I have however had water in the bilge historically which may have contributed to thread degradation over time.
Boat is a 1988 Catalina 34.

[GordMay]

... Why remove/replace if I can attain torque specs? ...

Because you may have lost spec’d bolt diameter, and bolt may have been over-stressed in stripping.

[Franziska]

I'd leave the bolt put and use a second nut.
Trying to remove it will be a huge effort, only worth it if your insurance company complains or you can not sleep due to worrying.

How did the stripping occur?
How does the overall bolt pattern look like? Which bolt is it? Front or trailing edge, or side of keel?

One reason is that keel bolts have usually a fairly big amount of safety in their design calculations, further the bolt does not show signs of corrosion.
The bolt has been stripped to the bottom of the thread which is equal to its solid diameter at its thinnest location anyway.

One thing I wonder more about is what looks like a hairline crack in the glass beside the bolt (about one bolt diameter away). Might be the picture though...

This is just my thoughts looking at it and not a legally binding professional advice. :-)
The decision is up to you!

[captainjay]

You should look at a few of these Google images and decide how to proceed.
https://www.google.com/search?q=cata...D2bv6iUo9TlwM:

It does not look like you have j bolts just threaded rod. The damage is either gauling or corrosion. Gauling would mean you just lost the threads. Corrosion is a much more serious problem. I wouldn't bet my boat or life on gualing. I would drop the keel and replace them all.

Jay

[a64pilot]

Originally Posted by RaymondR

I'd put a couple of more washers under the lowest nut to ensure that you have good threads over the full depth of the top nut.

If you chose not to replace the stud, this is your best course of action.
Reason is if you use two nuts, the first may cause enough interference that the second won’t properly torque. You torque bolts to stretch them of course, and the first nut may keep you from stretching the stud the proper amount.

[DougR]

-Replace the skimpy washer with a much more substantial stainless plate to spread the load.
- Drill out or otherwise remove the internal threads from the lower nut to be sure it doesn't catch any thread and acts as a spacer only.
- install a second nut and washer and torque to spec.

DougR

[jimbunyard]

The drilled-out nut over a more substantial plate with a lockwasher and new nut would be my choice as well, with the addition of flattening the seating area (grinding off the gelcoat) under the plate. If there is substantial 'wasting' of one bolt more than others, there would likely be a different sound resulting when they were struck with a hammer.
Also, if you can't torque it to spec, it probably needs to be replaced. (though that doesn't seem to be the case here...)

[US1Fountain]

Is that a nut under the white stuff? Looks like a hex outline. Also, what is it the that the nut is bottoming out against? Appears to be the side of a nut.

[Swift Drift]

Thanks for all of the great advice!

The Location of this keel bolt is one keel bolt forward of the trailing edge. It is in a single file layout, followed by a series of double keel bolts (side by side) moving forward.

There is not a crack in the bilge, what you are seeing is the outline of a large washer that had gel coat/resin spread over it at the factory.

The comments about making sure the "bottom nut" doesn't interfere with my toque specs makes sense.
I don't believe it is corrosion. In person it's more obvious than in the picture. "Gauling" or stripping of the threads seems to be the culprit. Plus, this is the only keel bolt with this issue (I know that isn't proof but makes it less likely).

[chris95040]

I think I see cracks, too. I'd want to really know what was going on there.

Hey, for folks with J-bolts, couldn't you just get off cheap by drilling and tapping new bolt holes from inside the bilge?

[njoynthewater]

Are the threads stripped in the nut or on the stud? Split the nut to remove it to check so you don't risk damaging the stud if the nut is spun off. It should come off either way

[Adelie]

Here’s a really scary question. Where did you get the spec to tighten the bolt to?

I replaced my keelbolts recently and what to torque them to was a big question. I did a lot of research and got conflicting info from different boat manufacturers about what torque to achieve.

Since fiberglass is in the grip of the bolt you can’t torque to the max the bolt will take.

What diameter bolts and what torque did you tighten to?