Caulk Recommendation

[dgsail]

I removed and replaced the threaded metal mast antenna connector that runs from the top of the deck through to the hull headliner inside the cabin. (CD 26). I filled the hole with west 610 2 part epoxy and re drilled it. I installed the new connector and now when it rains, water is coming into the cabin. I suspect I need to caulk.

Could I place a piece of butyl tape on top between the deck and the nut?
or Should I use a silicone caulk? If so, am I caulking just the top or trying to get caulk into any air space inside the hole?
Keeping in mind that the part may need to be replaced again in the future.

[mashenden]

If it were mine, I would try either butyl tape or 4200, depending on what was available. 5200 has more adhesion so it would be more difficult to remove in the future, which is why I would go with 4200. W-mart sells a non brand version in a small tube in the boating section. It is priced better than marine stores - price is of particular concern to me on this product since I rarely need a full tube and it tends to set inside the tube once its open (over a couple of months).

I would suggest using a large drill bit to take the edge off the hole - Not all the way through but just enough to take the edge off. This makes an area for the sealant to make a good gasket, and not squeeze out when tightening. Then apply the sealant of choice to the connector and some in the hole if possible. This should make a good watertight connection.

[John Stone]

I would never use 5200 on anything that has to be taken apart in the future. IMO, never use silicone on your boat. 3M 4000 is appropriate. Sikaflex makes a wide variety of compounds suitable for this project as well.

As Matt suggested you want to gently chamfer the hole so there is space for the bedding compound to be forced into. I have used many rolled of butyl rubber on my boat and it is good stuff but is normally only appropriate when there is a nut on the back side that you can tighten.

I disagree that you should not tighten down. You want squeeze out.

[Astronomertoo]

I removed and replaced the threaded metal mast antenna connector that runs from the top of the deck through to the hull headliner inside the cabin. (CD 26). I filled the hole with west 610 2 part epoxy and re drilled it. I installed the new connector and now when it rains, water is coming into the cabin. I suspect I need to caulk.

Could I place a piece of butyl tape on top between the deck and the nut?
or Should I use a silicone caulk? If so, am I caulking just the top or trying to get caulk into any air space inside the hole?
Keeping in mind that the part may need to be replaced again in the future.

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An alternate method is to use a replaceable, reusable deck penetration like a waterproof "clam" gland which you can cauld down and insert the cable thru. West Marine and Defender sell varius sizes which are good for all kinds of winring including mast, solar, and mast wiring. In addition, you must seal any exposed electrical RF connection to the antenna. For example, if you have your coax cable exiting the mast near the deck(for easing the disconnection), you can mate it to the above deck cable outside the bottom of the mast (if not internal inside the mast), and weather seal them together using back and forth wraps of the more flexible Scotch 33+ black tape, such that the cable connections will never get wet, but are easy to disconect when you need to remove the mast. I have never had any water in my connections.
The reason both (any!) silicone sealant and 5200 caulk (which is not meant to be a sealant) is so abhorent on a boat, is they are both permanent, plus silicone sealant will prevent epoxy and paint from bonding well to boat parts. You can not even sand it off, and it causes problems for subsequent owners.

[mashenden]

...I disagree that you should not tighten down. You want squeeze out.

Good clarification. Some squeeze out is good. My concern was with not chambering, which causes much of it to squeeze out, leaving a thin film that fails quickly.

[John Stone]

Lots of the how-to books suggest that you make light contact with bedding compound then let it cure then tighten down. The problem is that if the fitting can move it will eventually separate from the bedding compound. The key is the chamfered hole in the deck the shaft of the fastener passes through. That little funnel shaped space compresses the bedding compound in around the fastener and greatly reduces the chance that water will make it through.

[mashenden]

Lots of the how-to books suggest that you make light contact with bedding compound then let it cure then tighten down. The problem is that if the fitting can move it will eventually separate from the bedding compound. The key is the chamfered hole in the deck the shaft of the fastener passes through. That little funnel shaped space compresses the bedding compound in around the fastener and greatly reduces the chance that water will make it through.

Yeah, I've never felt like that was a good approach, particularly if the screws are involved in the seal. It seems that tightening would break the seal.