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Prop strut caulking?

While my boat is out of the water for gelcoat and rigging repairs I have been painting the bottom and installing a new folding prop. While inspecting and cleaning my prop strut I noticed that where the strut meets the hull there was a flexible silicone-like caulking that was no longer adhered to the strut. I decided that I should peel it away and see what was underneath. From the looks of it the caulking was just fairing. It certainly wouldn't be sealing anything. Underneath the caulking is just gelcoat hull and resin filling the strut penetration.

On my last boat the strut just exited the fiberglass, with no caulking of any kind.

So once I remove the old material, what product should I replace it with? Should I use another flexible material like I took out, or should I fill the area and fair it with something harder? Perhaps an epoxy putty?

The first picture shows the old caulking, and the second picture shows what is underneath it. I was able to pull the caulking off with my fingers with little effort.

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Re: Prop strut caulking?

If you're sure the strut is properly watertight on the inside, I'd use 4200 to fair it on the outside. If you peeled it off, with your finger, the surface probably wasn't well prepped. Be generous with the fairing. Most underwater parts call for 5200, which might be wiser. However, it's harder to replace and I don't think flexes quite as well.


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Re: Prop strut caulking?

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Originally Posted by Minnewaska View Post
If you're sure the strut is properly watertight on the inside, I'd use 4200 to fair it on the outside. If you peeled it off, with your finger, the surface probably wasn't well prepped. Be generous with the fairing. Most underwater parts call for 5200, which might be wiser. However, it's harder to replace and I don't think flexes quite as well.
So, what is the purpose of the fairing, or caulking, or whatever?

Asking because I may be in the same situation; I have the same stuff at the strut, I think, but never had the guts to pull hard on it...
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Re: Prop strut caulking?

Iíve used epoxy fairing compound on that joint in the past on my boat. If I recall correctly Iíve had to rework it twice in the 11 years Iíve owned the boat....once in the initial haulout when I bought her and again about a year ago. A more flexible sealant like 4200 might work better?

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Re: Prop strut caulking?

Quote:
Originally Posted by MastUndSchotbruch View Post
So, what is the purpose of the fairing, or caulking, or whatever?

Asking because I may be in the same situation; I have the same stuff at the strut, I think, but never had the guts to pull hard on it...
To avoid a leak, if the primary sealant were to crack or become otherwise compromised.
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Re: Prop strut caulking?

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Originally Posted by Minnewaska View Post
To avoid a leak, if the primary sealant were to crack or become otherwise compromised.
Thanks.

Hmm, given the state of the rubbery stuff on my boat, I guess the primary sealant is doing just fine
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Re: Prop strut caulking?

Yeah it definitely was not intended as the primary sealant, it was intended to clean up the rough area around the penetration. After consulting with the guy at the boatyard who agreed with using 4200 I cleaned up the area, roughed up the smooth parts and filled the area with 4200. It's not perfectly fair, but it is better than it was.

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Re: Prop strut caulking?

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Originally Posted by SchockT View Post
Yeah it definitely was not intended as the primary sealant, it was intended to clean up the rough area around the penetration. After consulting with the guy at the boatyard who agreed with using 4200 I cleaned up the area, roughed up the smooth parts and filled the area with 4200. It's not perfectly fair, but it is better than it was.

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What's the hole for in the strut? Zinc?
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Re: Prop strut caulking?

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Originally Posted by MastUndSchotbruch View Post
What's the hole for in the strut? Zinc?
Yes, I've never pot a zinc on my strut before, but this boat came with one so I might as well keep putting one on since the hole is there.

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Re: Prop strut caulking?

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Originally Posted by SchockT View Post
Yes, I've never pot a zinc on my strut before, but this boat came with one so I might as well keep putting one on since the hole is there.

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