The Boating Forum - Best caulk for boat seams

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View Full Version : Best caulk for boat seams


scallywag
05-19-2010, 04:56 AM
Anybody have any thoughts on the best marine caulk to use on exterior boat seams.
I have a 25yr. old fiberglass lobster boat that has seams that need to be recaulked
around the pilothouse. My concern is future removal and non-yellowing. I'm
thinking a Boatlife product but notsure which one. Thanks


bfox76
05-19-2010, 05:14 AM
The 3M 4000 UV is a great product, but it does yellow. I used it on all my hatches not too long ago. It provides great flexibility and movement with the boat, but if water sits in an area on a joint, it will yellow.

3M 5200 will be too permanent, IMO. I used it when I put my T-Top back on and have noticed that it yellows as well.

I asked the same question on here, not too long ago. Here is the link: http://www.thehulltruth.com/boating-forum/272219-what-best-marine-sealant-silicone.html


Good Luck.

CaptainJR
05-19-2010, 05:39 AM
I recently used Boatlife Life-Seal on my exterior seams. They also have Life-Caulk. I use the 3M products, 4000 or 5000 series, when I need an adhesive to bond two materials together. But I think you are just looking to seal a seam. I would not use an adhesive for that.


TwentyFourSeven
05-19-2010, 06:39 AM
Ordinary white silicone is about the best thing to use and it will never yellow.

2dogs1949
05-19-2010, 06:48 AM
Boatlife- Life Seal is all I use for non adhesive applications. Both above and below the water line. Every time I pot a hole in my boat it gets Life Seal no matter where it is.
" I put that $h_t on everything"

Whaler1777
05-19-2010, 07:04 AM
Never put household "ordinary white silicone" on a boat... Let alone a commercial Lobster boat... Use 4000 the uv resistance and the fact that you can remove it if you need to...

TwentyFourSeven
05-19-2010, 11:55 AM
Never put household "ordinary white silicone" on a boat... Let alone a commercial Lobster boat... ...


Why not, I do it all the time. Works fine and never yellows. I put some on my boat two years ago and its still there.

bigfished
05-19-2010, 12:59 PM
Why not, I do it all the time. Works fine and never yellows. I put some on my boat two years ago and its still there.

Because it doesn't have the word "marine" on the label !

TwentyFourSeven
05-19-2010, 07:24 PM
Because it doesn't have the word "marine" on the label !


Thats the only reason.

caltexflanc
05-19-2010, 07:37 PM
Silicon will seep into your gel coat and make any future painting virtually impossible. Silicon has no business EVER being applied to exterior gelcoat and fiberglass. And yes there is "Marine" silicone sealant; use it inside or for things like sealing polycarbonate windows to aluminum frames.

BTW, you can paint over 5200/4200 etc, otherwise they will yellow.

George
Hatteras 56MY
Boston Whaler 130 Sport

fishinmaniac
05-19-2010, 08:12 PM
I bet silicon is just fine but if it makes you warm and fuzzy inside then pay 4X more and use "Marine" silicon. :roll

caltexflanc
05-21-2010, 06:55 PM
Marine or not, it is not fine on gelcoat or any painted fiberglass surface. Period. Why not use the right thing?

fishinmaniac
05-21-2010, 08:25 PM
Have you tried both, just asking?

TwentyFourSeven
05-23-2010, 02:04 PM
Marine or not, it is not fine on gelcoat or any painted fiberglass surface. Period. Why not use the right thing?

Silicone is the right thing it does not yellow, everything else does.

caltexflanc
05-23-2010, 03:57 PM
Well, good luck with that. There are plenty of things that work better, don't yellow and are not silicon. It's your boat.....

and yes I have seen directly the damage that silicone sealants do to gelcoat and painted fiberglass.

Mr. Demeanor
05-23-2010, 04:09 PM
The problem with silicone is that nothing will ever stick to that area again. You will never see a tube of silicone anywhere near a body shop for that very reason.
I actually think doing the seams in black might look nice if they were all sone that way from the beginning. My boat is black and white so it might look nice.

TwentyFourSeven
05-23-2010, 07:31 PM
Well, good luck with that. There are plenty of things that work better, don't yellow and are not silicon..


Such as? ;?

cknlg1
05-12-2013, 08:15 AM
This has created several questions...do you use silicone, marine silicone or something else. The biggest question is my boat is new and needs fixed. There are several gaps under my bumper rail all the way around. How do I know what the factory used before I start applying something else? It looks like a silicone of some kind.



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