Best Black Caulk?

[tank1949]

I am mounting MC transom assemblies after months of repairing and rebuilding what an incompetent marine surveyor missed. I want to use some sealant on my new Bravo transom seals just to be sure that any imperfections do not cause issues when boat gets into water. I am hesitant to use 5200 because it will require major work if I have to disassemble later on. I want to caulk area between metal transom assembly (gimbal housing) and stern. Both metal and glass have been painted and are "slick." Any suggestions?

 

[alldodge]

Suggest do not use any kind of calk, its not needed if the surfaces meet the specs for the transom, your good. If the transom needs flattening, use something to build it up and smooth flat (JB weld, or other). Then just use the gasket and torque to spec



But to answer your question, if you have to use calk, I would suggest 3M 4200

But its not black

 

[tank1949]

thanks, and I have done all that and transom is within specs that you provided. However, gimbal housing assembly was very pitted due to salt water corrosion. I had professional welder do as best that he could grinding and welding and trying to smooth out the welded peeks and valleys. There are plenty of used saltwater used Bravo assemblies for sell on the web. I could not find a fresh water used one that didn't have to be completely overhauled. My gimbal ring is tight. The only corrosion was at lower seal area. I found several fresh water used Y pipes and inner plates but no Bravo gimbal assemblies (worth the money) . I believe that my re-welded Bravo is strong, but a pin hole leak will cause me headaches. In addition, every transom assembly that I have removed (mostly Alphas) I have noticed that the seal has been flattened over time. I am hoping that added caulk will provide additional peace of mind. I kept log and photos of my work if I sell this boat year from now.

 

[Iskander-M]

Sikaflex 292i

https://www.sika.com/content/corp/m...market/product-catalogue-marine/sikaflex.html

 

[tank1949]

Sikaflex 292i

https://www.sika.com/content/corp/m...market/product-catalogue-marine/sikaflex.html

Sounds like a 5200 alternative? Until now, I had never heard of it. Thx

 

[Iskander-M]

I used this Sikaflex 4 years ago sealing the gap between the cast iron keel and fibreglass, under waterline. Still perfectly sealed and looks like hard rubber now. Would definitely recommend it, comes in white or black, about £12.00 a tube.

Just an advice, when you work with any Sika sealants or adhesives always wear disposable latex gloves. Once it’s on your skin for more than 5 min you could not remove it with anything like MEK or acetone. So the next 2 weeks anyone looking at the black marks on your hands, neck and face could tell you was working on your boat

When I was working for Dufour in La Rochelle (France) we used Sikaflex for all sealing jobs above and below the waterline, the life expectation was about 20 years if I remember well.

 

[tank1949]

I used this Sikaflex 4 years ago sealing the gap between the cast iron keel and fibreglass, under waterline. Still perfectly sealed and looks like hard rubber now. Would definitely recommend it, comes in white or black, about £12.00 a tube.

Just an advice, when you work with any Sika sealants or adhesives always wear disposable latex gloves. Once it’s on your skin for more than 5 min you could not remove it with anything like MEK or acetone. So the next 2 weeks anyone looking at the black marks on your hands, neck and face could tell you was working on your boat

When I was working for Dufour in La Rochelle (France) we used Sikaflex for all sealing jobs above and below the waterline, the life expectation was about 20 years if I remember well.

Thanks for your advice. I emailed Sikaflex for recommendation, since there are so many Sikaflex options. But, they have yet to respond!