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Q: I have a Catalina 27 and my keel bolts are weeping. There’s a small crack (the Catalina Smile) at the forward end of the keel, between the keel and where it attaches to the hull, that’s allowing the saltwater to corrode the keel bolts and weep slightly into the bilges. Catalina offers a kit with stainless keel bolts designed to sister the existing non-stainless keel bolts. I’ve heard this isn’t a legitimate fix, but I know several people who’ve done it. My boat isn’t worth spending a whole lot of money to remove the keel and start from scratch. What do you suggest?
A: As you have already found, a slow leak around a keel bolt or a poorly sealed bolt in a wet bilge will eventually lead to corrosion. If the keel bolts are mild steel, as yours are, the corrosion will appear as the familiar rusting of bolts and nuts, which eventually lose strength as they are eaten away.
In most cases, though, keel bolts are made of stainless steel, which corrodes when the surrounding moisture becomes deoxygenated. Stainless steel in water normally has a ready source of oxygen except when the water becomes stagnant, in which case the stainless reacts with itself and begins to disintegrate. With keel bolts, this corrosion is almost always above the level of the lead. The accompanying photo shows the typical pattern of corrosion.
To prevent corrosion for both stainless and mild steel, the keel-to-hull joint and the bolts must be completely sealed. Lag bolting the keel through the keel stub to sister up the corroded bolts raises a number of important concerns. Keel bolts aren’t lagged in the first place because lead is malleable (soft) and likely won’t support the required 40 times the static load that bolts are designed to carry (especially important under abusive conditions). Keel bolts are usually bent into a “J” shape or welded into a cage and then cast into the lead. This is much stronger than lagging. Most repair yards would be uncomfortable with the proposed fix, as the cause of the problem is not rectified. Sure, it’s inexpensive and may extend the life of an otherwise unusable boat. The underlying problem, however, isn’t addressed by simply adding more fasteners. The reliability of the repair will always be in question, with inevitable concern regarding the boat’s safety.
If the keel is leaking, the condition is unlikely to change without the removal of the keel to re-bed it. Existing bolts will continue to corrode (regardless of material type) and the new lagged-in ones will, in time, also be compromised.
A proper repair involves removing the keel and re-bedding it, as well as some delicate welding and rethreading of the existing keel bolts (if stainless steel). If the existing keel bolts are mild steel and heavily corroded, it may well be impossible to repair them.
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