3M Marine Adhesive/Sealant Fast Cure 4200, 06564, Black, 1/10 Gallon

A little on the expensive side but!; Well worth the use in below the waterline applications. A few things to note and be aware of. The difference between the 4200 vs 5200 is this; the 4200 is not "permanent" as the 5200 is for one. So if you use this for thru hull applications that's a good thing if it's an item that one day will require removing or servicing. Also the 4200 does not have the shear- structural strength as the 5200 does, thus you may need to consider a mechanical attachment such as a well/hull nut (which you'll want to set and attach with the 5200) I would not rely on the 4200 for pure structural attachment on anything. As far as water tight, durable and ease of application, this is a great product. Again, just understand your application needs. Also once opened, "air" (02) and exposure to the atmosphere starts to "cure" the product, even with a cap on or plugging the nozzle. A great suggestion I learned was to warp the product in ceran-wrap tightly and keep stored in the freezer. The cold "frozen" air great mitigates air and leaves the product well preserved. I found this to be true and really works. I used the product 2 weeks later on another project. I pulled it out of the freezer and let it get acclimated to room temperature which took less than 2 hours. It flowed smooth and kept all it specified properties and performance characteristics. I mention this as expensive as this product is, don't let it go to waste!

Great product... IF YOU GET ONE NON DAMAGED.First one was shipped in a plastic bag, thanks amazon. Was dented up and leaking upon delivery. Second one fortunately came in a box and was fine. Was annoyed that amazon wanted the first one shipped back even with pictures of the damage as it belonged in the trash can. Had to make a trip to drop it off...That said this is good stuff for its intended marine purpose. Just plan to order it ahead of time as you may well get a damaged one.

This product was great, got it yesterday already used today 👍

I wish I could have found a smaller size. The sealant works great, looks great, wears great

I gave the sealant to my repairman who was fixing my boat and I guess it worked ok. There were no negative comments from him but then the boat has not hit the water yet...

Product did not come with the plastic nozzle rendering it useless. Caulk manufactured in July 2024. If you want the freshest batch maybe look elsewhere.

This stuff cures solid so fast and is very good quality. Use it for diving suits like Hot H2O suits and Wetsuit seems for commercial diving and you can’t beat this stuff

Very black, but does have UV protection in it.I’d like to see it in more colors . I did have a rubberized sealant effect.