How to check rusty keel bolt integrity

[Dpmmvc]

I’m attaching a photo of a compartment in my bilge that houses 3 of my 8 keel bolts. This compartment is where my shower drains into. There is a puddle of soupy rust water and the bolts I believe only contain surface rust... My question is ; how do I check the bolts for damage beyond surface rust?

[tkeithlu]

Most readily, with a wire brush or other way of cleaning the surface rust off so you can see the good metal. Beyond that, it's take one off while sitting at dock, checking the threads, and then replacing it (at the right torque!) before taking the next one off.

They look pretty good to me.

[Bill O]

What kind of boat, age, etc.? Any known keel bolt issues w/your type of boat?

Would try to clean up the keel bolts (initially wipe down) to see if they are the source of the rust or is it from poor quality hose clamps. Cheap hose "SS" hose clamps will generally have an OK band but then use a steel adjustment screw.

Use a magnet to see if you have steel screws on your clamps. If so change them out w/better hose clamps (again use magnet to check the hose clamp/screw before purchasing).


Bill O.

[NSboatman]

At a glance, that looks just fine to me- perfectly normal. There is superficial rust, yes, but no visible flaking, the nut is still hexagonal, and thread forms are visible.

Dry it out (shop vac and rags) get. Good light on it, then tap it with a hammer and chisel/rough screwdriver to make sure it is still solid and no huge chunks come off. Then Wire brush it, and use a good rust converter, then a spray can of heavy zinc cold galvanizing.

The other response about boat history and previous knowledge of histories is absolutely valid though. Double if you actually see bleeding from the keel-hull joint when hauled.

[Dpmmvc]

Thanks Bill O. I never thought of the rusty water coming from another source. The boat is a 1988 Catalina 30. The keel to hull joint looks great from the outside of the boat. No exposed joints or “smiles.”

[MartinR]

I agree, the keel bolts look perfectly fine. If you wire brush them, it is good practise to passivise them afterwards with some citric acid.

[boat driver]

If you inspect those in that compartment and they are clean- then you have eliminated a concern of electrical or chemical decomposition at the nuts/exposed area. The true problem is inside the joint- and can not be readily visually inspected.
As previously mentioned- If any type of keel movement when boat is hauled will show stretch of materials. As water drains and dries- is it rusty streaks on keel? take into account the bottom paint colors/materials.
If in one place then maybe- if lots of rusty water then maybe further research with boat yard manager and a surveyor. Often if a surveyor around opinion is worth a cash tip-
If clean on top at nuts, try torquing. If all come up same feel then prob ok. If one comes up easier or out of sync with others- start looking for stretch in bolt- a sign of weakness.
Front and back bolts tend to be the first to show sign. (but not always)
Only true ways of checking is xray, ultrasound, or dropping keel.

[Cadence]

I think you are fine. hit them with some ospho to curtail rusting, Stay the hell away from them with a wrench.

[zstine]

You should absolutely torque them with a wrench! a big one! Not sure why anyone would say "stay the hell away from them with a wrench." Torquing keel bolts is part of standard maintenance on a boat and something you should do annually IMO. Anyway, torque the bolts per manufacture spec, which is typically 60% yield give or take. This is much higher loading than operational loads. It is important to keep them properly preloaded to reduce the effect of cyclic loading. If they don't break during torquing, then pretty confident you are good to go.

[Cadence]

With the rust, putting any torque on it may cause the anchor in the keel to come loose creating a problem that didn't exist. Maybe soaking it and rocking it back and forth?

[zstine]

Originally Posted by Cadence

With the rust, putting any torque on it may cause the anchor in the keel to come loose creating a problem that didn't exist. Maybe soaking it and rocking it back and forth?

If the rust has caused the bolt's anchor point in the keel to come loose, then the problem is there regardless of whether you torque on not. If you don't torque, you just don't know your keel is about to fall off. Torque them, if they pull out, then you have to fix the problem. Torquing them does not "create a problem that didn't exist". It simply identifies if a problem does exist.

[Cadence]

Originally Posted by zstine

If the rust has caused the bolt's anchor point in the keel to come loose, then the problem is there regardless of whether you torque on not. If you don't torque, you just don't know your keel is about to fall off. Torque them, if they pull out, then you have to fix the problem. Torquing them does not "create a problem that didn't exist". It simply identifies if a problem does exist.

Maybe I just don't understand torque. It . in my understanding, is to apply longitudinal pressure to the anchor not rotational although it is measured as a rotational force but is placing a longitudinal force on the anchoring bolt via the threads. Threads siezed there is a problem.

[ferrailleur]

Originally Posted by Cadence

With the rust, putting any torque on it may cause the anchor in the keel to come loose creating a problem that didn't exist. Maybe soaking it and rocking it back and forth?

agree.... don't fix it if it ain't broken!

[zstine]

Originally Posted by Cadence

Maybe I just don't understand torque. It . in my understanding, is to apply longitudinal pressure to the anchor not rotational although it is measured as a rotational force but is placing a longitudinal force on the anchoring bolt via the threads. Threads siezed there is a problem.

The original post said nothing about "threads being seized". But yes, of course you should use WD40, PB blaster or whatever to penetrate the threads. Many torque specs will identify a lubricant, or lack thereof. Looking at the photos, I don't expect seizing to be an issue as it just looks like surface rust likely caused by contamination from other sources. Yes, you are right that torque is to apply tension in the bolt. And if they are seized, applying the spec'd torque should not create any damage. It may not cause any rotation of the nut.... BUT if the spec'd torque causes say, the bolt to spin vice the nut, then you have an issue that should be addressed. Again, not caused by the torque, but one already there.

[Cadence]

[QUOTE=zstine;3054529]The original post said nothing about "threads being seized". But yes, of course you should use WD40, PB blaster or whatever to penetrate the threads. Many torque specs will identify a lubricant, or lack thereof. Looking at the photos, I don't expect seizing to be an issue as it just looks like surface rust likely caused by contamination from other sources. Yes, you are right that torque is to apply tension in the bolt.[/QUOTE

Hopefully never sieve was used.