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Old 01-03-2021, 14:38   #1
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sealant for bolts in skeg!

I have quick question for the group I have my boat in the hard I removed the bolts in the skeg/ shoe. they had a black sealant on them. I don't think it was 5200 ( because they were that hard to remove ). I would like to get recommendations as to what to use to install them again.

thanks

D
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Old 01-03-2021, 23:33   #2
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Re: sealant for bolts in skeg!

I don't know what the black sealant is as there are many of them. Of course you need to use a good sealant otherwise water will get in and it will cause crevice corrosion.

This article is well worth reading.

Crevice corrosion – Cox Engineering
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Old 02-03-2021, 05:48   #3
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Re: sealant for bolts in skeg!

While not doubting Coopec43's recommendation, I can't see what materials you are working with.
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Old 03-03-2021, 20:05   #4
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Re: sealant for bolts in skeg!

Tkeithlu The bolt are cleaned so no sealant is currently on them. The bolts are SS and the skeg is bronze.
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Old 04-03-2021, 05:58   #5
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Re: sealant for bolts in skeg!

coopec43 is correct, if brief.

OK. Your concern is corrosion, and there are two ways to deal with that. One is a grounded anode which you undoubtedly have nearby. The other is keeping electrolite, in this case seawater, out of contact with the interface. Just about any isolating goo will do the job.

Choose one of high quality, such as with a high years claim, as in "30 year," but not 3M 5200 if you ever want to separate them again. Spread evenly, bolt into place, but do not tighten. Wait until after the stuff has set to torque it. That's important. If you tighten on wet goo, you just cut through it, and don't get any isolation or ability to push water out, and the goo may loosen. Let it set, then do that last half turn, and you get a compressed gasket. On to the next task in your haul out.
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Old 04-03-2021, 07:01   #6
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Re: sealant for bolts in skeg!

Silicon bronze bolts, silicon bronze backup plates, extra heavy nuts and 5200.
Thatís how I have done it and have seen no issues after decades in the water.
I donít think itís a good idea to use stainless.
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Old 04-03-2021, 07:27   #7
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Re: sealant for bolts in skeg!

5200 is scary. not on my boat. at some point down the road someone is going to have to remove those bolts again, be kind.

use Sikaflex 291 or preferably 291 LOT (Long Open Time) for underwater. just installed my thru-hulls with Sikaflex 291 LOT. the LOT gives you extra working time, and for thru-hulls and struts and the like things can get complicated where the extra time is needed. somewhere between 4200 and 5200 but you can remove it.

3m 4200 would work. white 4200 yellowed on me. id stay away from 4000uv and Sikaflex 295uv not the best for this. I use 4000uv for way above waterline thruhulls and mast hardware, ect. places exposed to sunlight more.

Its concerning the mixing stainless bolts with bronze. SS is not really a good metal underwater or places without oxygen. two different metals in a electrolite (seawater) make a battery. switch to silicon bronze or aluminum bronze bolts. i believe silicone bronze is better for underwater.

because you had SS Bolts on bronze i wouldn't trust the stainless anymore. might want to check the bronze and see if its discolored. good recipe for crevice corrosion. replace the bolts with new regardless. i highly recommend Bronze!
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