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.

 

[Boatsb]

I don't believe 550 is for below the waterline. Double check before you find out the hard way.

 

[spartonboat1]

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.

Jim:
Yes, for a 1972 boat, new bolts seems indicated, esp. Silicon-Bronze.

I have not researched the 3M 550, so if you have findings, would be interested to hear.

 

[rustybucket]

I don't believe 550 is for below the waterline. Double check before you find out the hard way.

550, 4200 and 5200 are all rated for above and below waterline uses. I'd venture to say that almost every thru-hull fitting in a production boat leaving the factory today is sealed with 550. According to 3m it is the appropriate choice for this application.

5200 is more of an adhesive than a sealant. 4200 is more of a sealant than an adhesive. 550 is right in the middle of them with both good sealant and adhesive properties. 3m rates 5200 as 'good' for sealing, it rates 550 and 4200 as 'Best Choice' for sealing. In this particular application he needs extra 'sealing', the sealant is not doing anything to 'hold' or 'bond' the screw, the mechanical fasteners are handling all the bonding.

I've pulled apart many parts 'sealed' with 5200 only to find that water was getting in, at least partially in most cases. 5200 is great for gluing things together, not so much for sealing them.

By far the best thing about 550 is that it is rated as removable, 5200 is not. Also 550 is paintable in an hour and cured in 24hrs. 5200 can take days to fully cure.

If you want the word straight from 3m here is a link to the brochure for the products. Open this document and do a find/search for 'below' it will lead you straight to the excerpt. There is also a good comparison chart on page 6.

https://www.google.com/url?sa=t&rct...5 Lo Res.pdf&usg=AOvVaw1SXD9mn9e2k7MADAhl80AF


3MTM 550 Polyurethane
Adhesive Sealant Fast Cure
• Multi-purpose adhesive sealant
• Paintable
• Above/below waterline use
• 60-minute skin time

 

[Cricket]

At the boatyard we use they hauled a 3 year old 80' Viking to remove a keel pocket mounted transducer, huge 3kw chirp transducer.
It took the crew Viking sent 2 full days to get it out of the keel, I assumed it was put in with 5200, no matter there was so much of it there that a lot of it had not cured.
Now after Rusty's post i'm not sure if it was 5200 or not. They did put the new one in with 5200.

I have to somewhat agree with Rusty about the sealant qualities of 5200.
Years ago an old timer told me he thought 5200 wicks water, and I think I've sort scene that a few times.
We've been using Sikaflex products when we can as of late.

 

[rustybucket]

I have to somewhat agree with Rusty about the sealant qualities of 5200.
Years ago an old timer told me he thought 5200 wicks water, and I think I've sort scene that a few times.

I redid all the thru-hull fittings, swim platform and exhaust flanges on our old Shamrock 246. They were all bedded with 5200. Not only was it a complete nightmare to get the fittings out (most had to be destroyed to remove) but I saw a lot of what you are saying, hard to describe, like it was just wicked up toward/to the fittings in various places. I'd say half the fittings were well sealed, the rest not so much.

5200 is a fantastic product, but like any product it has it's strengths and weaknesses. For some jobs it is the absolute correct choice, for others not so much.

 

[dsharp]

BoatLIFE Life-Calk polysulfide marine sealant. You can use this product. years ago we used Thiokol, before there was anything in a tube to use. Be sure and leave a nut on the top of the bolt if you have to drive it out from the top so you can straighten out the threads. Look closely at the strut where it meets the hull to see if the seal has been broken. You may never have to remove a strut and probably wont, unless you hit something.

 

[spartonboat1]

550, 4200 and 5200 are all rated for above and below waterline uses. I'd venture to say that almost every thru-hull fitting in a production boat leaving the factory today is sealed with 550. According to 3m it is the appropriate choice for this application.

5200 is more of an adhesive than a sealant. 4200 is more of a sealant than an adhesive. 550 is right in the middle of them with both good sealant and adhesive properties. 3m rates 5200 as 'good' for sealing, it rates 550 and 4200 as 'Best Choice' for sealing. In this particular application he needs extra 'sealing', the sealant is not doing anything to 'hold' or 'bond' the screw, the mechanical fasteners are handling all the bonding.

I've pulled apart many parts 'sealed' with 5200 only to find that water was getting in, at least partially in most cases. 5200 is great for gluing things together, not so much for sealing them.

By far the best thing about 550 is that it is rated as removable, 5200 is not. Also 550 is paintable in an hour and cured in 24hrs. 5200 can take days to fully cure.

If you want the word straight from 3m here is a link to the brochure for the products. Open this document and do a find/search for 'below' it will lead you straight to the excerpt. There is also a good comparison chart on page 6.

https://www.google.com/url?sa=t&rct...5 Lo Res.pdf&usg=AOvVaw1SXD9mn9e2k7MADAhl80AF


3MTM 550 Polyurethane
Adhesive Sealant Fast Cure
• Multi-purpose adhesive sealant
• Paintable
• Above/below waterline use
• 60-minute skin time

Excellent update on the range of sealants. Very helpful, plus I will be sealing some windows and this range may contain a product for glass.

Thanks again!

 

[jim rosenthal]

I have not used 5200 for through-hulls for a while, as I've also had to remove fittings I installed with it. While Debond helps, it's still quite difficult. I use 4200 now and I've had no problems with it.

 

[spartonboat1]

I have not used 5200 for through-hulls for a while, as I've also had to remove fittings I installed with it. While Debond helps, it's still quite difficult. I use 4200 now and I've had no problems with it.

Yeah, Debond. Have a tube on the wall. Tried it once, gave it a lot of time. No Joy.

 

[spartonboat1]

Quick note on 5200 use. I installed Deck Boxes - were not the OEM Hatteras boxes. The Hatt originals are very stout. While these got good marks from he USCG, not in the league with Hatt's.

I installed them without fasteners and bedded on 3M 5200. Rode out 55mph winds, 12-15 seas (more?) for 40 mins, then 9-11 footers, - stayed nice and tight. I think the deck skin would pull up before these boxes would come off.

P.s., the Hatt rode well- never put the bow in the sea and water never got on the decks. Props came out of water and seas tried to broach me, but she never did. And this is a "little" Hatt. I am at 33K #'s; the new 45' 40 knot convertible is 55k #'s.