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gray_williams 11-13-2003 07:28 AM

Keel bolt issue
I have a question regarding what to do about my keel bolts.

I have a 1978 Catalina 25 with a cast-iron fin keel (1900 pounds). The keel is attached with 6 half-inch (I believe) mild steel bolts, attached with nuts in the bilge. The existing bolts are so rusted and flaking that not only are the threads not discernable, but large chunks of both nut and bolt have flaked off.

I do not know about the internal structure and reinforcement of the hull area to which the keel is atteched, but if anyone knows, please tell.

I''m pretty sure that this situation represents a problem, which I would like to fix before the keel joint starts leaking. My thought is to drill and and tap through the bilge and into the keel, then screw in bolts from above. Is this a good idea? How many bolts, how big (length and diameter) and what material (stainless doesn''t rust; mild steel is galvanically compatible) would be best?

The textbook solution seems to be to drill a hole from above, then drill a horizontal window in the keel to take a nut. This seems like a lot of effort in a cast iron keel; is tapping the keel itself OK (and feasible)? Any thoughts are appreciated.


aflanigan 11-13-2003 08:42 AM

Keel bolt issue
Wow, bad luck. Galvanic coupling is definitely something to keep in mind particularly if you are planning on keeping your boat long term.

Here''s a starting place; C25/250 owners forum on this very topic.

Looks like one alternative to trying to take out rusty old bolts is to "sister" them by simply adding new ones along side the old rusties. Good luck!

Allen Flanigan

soapstone 11-13-2003 11:43 AM

Keel bolt issue
In a previous life I did plumbing and electrical maintenance in a factory. We used to use a product called spraysalvo from chesterton that was nothing short of amazing. You could spray it on a piece of black pipe that was rusted through the bottom and come back in a few hours and it would just fall apart.

I suspect that it would do a pretty good job on those keel bolts if you kept applying it. Might save you some pain.

Back then, they didn''t sell retail, but you might be able to get it through your marina or something. Anyway, i noticed that their still selling the stuff out of an office in Mass. The link is

FloridaWriter 12-04-2003 11:24 AM

Keel bolt issue
IMO you should remove the nuts off these bolts, drop the keel, remove the bolts and replace them. Keel bolts shold be attached with nuts thru the boat''s keel and the nuts should be accessible so that they can be tightened if needed. Use tobin bronze for the new keel bolts and you will not have this problem again.

Jeff_H 12-04-2003 03:35 PM

Keel bolt issue
While I agree with you that keel bolts should be threaded at both ends so that the keel bolts can be easily removed for replacement, they almost never are, at least since the mid- 1970''s. Since then keel bolts have generally been a ''J'' shape and cast into the keels. Tobin bronze is great for lead and passable for cast iron but will electrolysize rather quickly with cast steel as was used on the boat in question.


FloridaWriter 12-04-2003 04:43 PM

Keel bolt issue
Have to disagree with you Jeff. First of all the Catalina has a cast iron keel not steel. Tobin bronze is considerably more noble. Not sure that the bolts on that boat are hooked in a J at the head, but new ones can easily be machined from a rudderpost or propeller shaft. Second, if the head or J of the bolts are sealed properly, the will never see moisture and not contribute to any electrolytic reaction. Finally, only if you are using something like bronze or 304 active stainless will you be able to adjust the nuts and tighten the keel.

FloridaWriter 12-04-2003 05:32 PM

Keel bolt issue
On second thought I would agree with you about the bronze and opt instead for hot dipped galvanized steel bolts or cast iron.

Jeff_H 12-05-2003 03:01 AM

Keel bolt issue
Actually, there had been very little ''cast iron used in this country since WWII. Most of what we call cast iron is low carbon steel. Low cabon steel is more rust prone and more electrolytically active than cast iron. When you cast J-bolts into cast iron the cast iron and bolts contract on cooling leaving a small crevice around the shaft of the bolts which permits corrosion. Replacing keel bolts in any iron keel is a tough proposition, been there, done that, wore out the tee shirt, but it is especially difficult with a keel that has J type bolts. If you were to use bronze bolts you would have three very different metals present, mild steel, higher carbon/higher strength steel (from the old bolts)and the bronze. That makes a near perfect battery. I agree with you about either using SS or Galvanized as perhaps a better choice than the bronze but, of course, what I am sure that you meant to say is that Monel would be an ideal choice given the various metals present.


roddandcara 12-05-2003 06:23 AM

Keel bolt issue
Catalina has an unadvertised program for replacing keels. Call them and get the details. Last I knew you had to remove the old keel, make a template of the old bolt pattern and ship the old keel back to the factory for a swap out on a new keel with your bolt pattern. When I checked this out three years ago (for my C-30) the price was around ten cents a pound with exchange of a lead keel. I would imagine they would not want your cast iron keel back so you could just send them the template and buy a new lead keel. The prices are very reasonable.....The other alternative is to do nothing and beleive it or not it may be the best alternative. I''ve been on boats where the nuts are similar in shape to a mushroom cap and the keels are still hangin in there. The early keels were bedded with a product similar to 5200 when the boat yard re-fastened my keel they took all the nust off and the keel was still hanging there. They had to use a sawzall to remove it. It finally came free when only two inches of bedding were holding it and then the fiberglass gave way not the bedding compound. My vote is to leave it alone or you''ll spend more money than it''s worth and never recoup your investment....

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