Sealing a Leaking Strut Fastener

[spartonboat1]

1972 43' DCFB: I located a very slow leak at a nut, where it attaches to a though-hull bolt, which is at at attachment for a strut. Although slow, it accumulates 2-3 gallons over a weeks time. Took a long time to spot it!

So for the time being, I was able to seal it by wrapping standard dental floss around and under the nut (true), which sealed it up. Then coated it with 3M 5200. It held all last summer (2019).

Before I go in the water, I wish to more correctly seal it, this Spring, 2020. However, should I push out the bolt and seal from the strut side, or would pulling the nut and sealing under it, around the bolt be acceptable?

Super simple question, but opinions please?

[Boatsb]

Always seal the outermost layer. Pull it and maybe all the bolts
They may be getting older and corroded.

[dsharp]

You need to remove the bolt and put the sealant of your choice on the shoulder of the bolt and under the head of the bolt. I should be a silicon-bronze carriage bolt. I wouldn’t use 5200. You’ll have hell getting the bolt out if you need to rebed the strut

[madhatter1]

Actually can only give a super simple answer. Yes, pull out and re- bed as as if new. But do all now. If one needs attention the rest are not far behind.

[spartonboat1]

You need to remove the bolt and put the sealant of your choice on the shoulder of the bolt and under the head of the bolt. I should be a silicon-bronze carriage bolt. I wouldn’t use 5200. You’ll have hell getting the bolt out if you need to rebed the strut

I do understand that if sealing the length of the bolt, 5200 is overkill and/or too much adhesion. Is 3M 4200 an alternative, or what are other choices?

[racclarkson@gmail.com]

Overkill is a word seldom heard below the waterline. Were you wishing to address this issue again?

[Cricket]

5200 for running gear, 4200 for non important parts. My guess is you may have something else going on, electrolysis to the bolts or the holes in the hull could have oblonged.
The suggestion to remove and recaulk all of the bolts is spot on, make sure to remove and replace 1 or 2 bolts at a time so the strut doesn't move.

[rustybucket]

If water was getting in you likely have crevice corrosion on the bolt anyways. Inspect closely when you get it out, I'd bet a dollar it needs to be replaced.

I would not use 4200 or 5200. For me, below the waterline for this application 3m 550 is the correct sealant.

[spartonboat1]

If water was getting in you likely have crevice corrosion on the bolt anyways. Inspect closely when you get it out, I'd bet a dollar it needs to be replaced.

I would not use 4200 or 5200. For me, below the waterline 3m 550 is the correct sealant.

Thanks for that reply!

[jim rosenthal]

For what the bolts cost, I'd replace them. And one at a time, like the man sez. 3M 550 is new to me. I'll have to look it up. I would have said 4200.