10 oz Marine Adhesive Sealant 5200 Fast Cure (White) - Permanent, Watertight Bonding and Sealing - UV Resistant, Above & Below Waterline - Compare to 05203 and 06520 FC M - by Berkland

The best.. strong and flexible. Stopped leaking in aluminum boat . Can be used for other purposes. I used it in the bottom of aluminum boat. And transom. Holds like i couldn’t believe. . It can be messy but it’s effective .

Worked great, stays sealed. Very waterproof so far.Will use again.

Perfect! This sealed up our cow’s water basin with one costing! We have tried everything else you can buy at the store and this is the only thing that actually worked! Buy this, you won’t regret it!

I used this to seal the windows in my house. It’s flexible and the seal worked better than I expected. I’ll keep an eye on it, but so far, I’m satisfied.

Very strong and easy to use excellent marine adhesive

Yes, as far as I can tell, it's as good as 3M. Zero shrinkage, turns into a hard rubber no matter how thick, paintable, flexible, adhesive. I use it for roof penetrations and caulking around windows, doors and siding, but it's rated for below the waterline. I did use the 4200 on my friend's boat, along the grab rails and hatches two years ago and it looks as good as the day I applied it. Really is waterproof and UV resistant.

We remodeled our home very recently. My wife's "change-order" involved extending the gerden hose station closer to her gardens. The 3/4" PVC piping was extended underground, the up though a stack of square CMUs to a hose bib. the cmu pedestal doesn't see alot of Arizona sun, but it does see enough (and monsoon!). This is a perfect solution to my close second (polyurethane). Absolutely perfect.

Started to notice water in the bilge, used this to make small repairs / seal leaking points on the exterior of my boat. Such as around rivets / screws, motor mount holes, accessory holes, seams, anything always under water. The boat is now dry as a bone, has held up beautifully for 6 months at least. This is the more permanent type of sealant, not the removable type. Really good stuff.