3MMarine Adhesive Sealant 4000 UV (05280), Medium Strength Flexible Waterproof Adhesive Sealant for Boats and RVs, UV Resistant, Cures in 24 Hours, White, 3 fl oz Tube

Best stuff ever for my camper.

This is THE product to use for marine applications when you don't want a permanent bond. The issue for me is, it's quite expensive and I only tend to use a fairly small amount at a time for repairs (e.g., installing a replacement stanchion). They tell you that you need to use it within one week of opening. This is only true if you want to dispense it through the nozzle. What I do for small jobs is punch a small hole in the side (I use a nail set or a nail), squeeze a little out using a caulking gun, and spread it with my finger (in a nitrile glove), then slap some tape over the hole. I've now been using one tube of a year on 6 small jobs, and I expect to do more.

This is an excellent product overall. While marketed as a marine sealant, it can be used in other applications where a waterproof, UV resistant seal is needed. I previously used this to seal around mounting brackets for solar panels on an RV roof. Now, I am removing dicor sealant around vents and other openings on the roof and using this instead. Based on my experience with it around the solar panel mounts, it seems to be far superior to dicor and similar products sold as roof sealant. It sets up quickly and acts as both a sealant and an additional bonding agent. I suspect it is strong enough to hold the solar panels by itself (I used VHB tape as well). The only downside I have found is it does not keep its shiny white appearance over time; it gradually turns dull aand yellowish, but as long as you use it where the appearance does not matter it is a great product.

This product, like all 3M products is outstanding. I used it to reseal a Pilothouse to deck seam that had developed some leaks. The previous seal/caulk had dried out, shrunk, and cracked. I cut it out and refilled the joint with 4000. I cleaned the area with acetone, masked off beyond the seam and applied 4000 with a caulking gun. The sealant flowed smoothly and filled the joint completely, easily resealing the leaky joint. This product is waterproof so cleanup is messy if you get it where you don’t want it. It does not smooth with a wet, gloved finger, merely smears. Apply enough to fill your joint and no more. Small overages will be “cleaned” up when you remove the masking. I applied the 4000 to a joint almost forty feet in length overall and the cure time is not so quick that I couldn’t easily pull the tape without pulling the caulk. It made an attractive seam and fixed the leak. Unlike 5200, 4000 doesn’t dry/cure so hard that it has to be ground out to remove it, but can be cut out with a knife at some future point if necessary.Unfortunately, this item was shipped by Amazon and though the box was undamaged, the interior bag was never sealed properly and the included nozzle was absent, having escaped through the improperly sealed inner bag before it was ever placed in the box. The fulfillment center never checked that the item was complete, because it was not. The delivery was quick and secure, the filling of the box was not.

I bought this product for sealing the lens to a Bomar hatch frame on our sailboat. It worked great and provided good adhesion to both the plastic lens and the metal frame. I then decided to use it when replacing a portlight window. It seems to have worked very well there as well. It seemed to be easier to work with than a competitor's product that I used on a previous portlight. Time will tell as to how well it holds up and remains watertight. I especially liked that the instructions on the tube said that cleanup can be done with isopropyl alcohol. As cheap as isopropyl alcohol is, I was excited to use a cleanup agent that worked well and that I didn't have to feel that I needed to use sparingly due to cost. the alcohol cleaned up the sealant very well. The only negative that I can say is that it is fast cure (as the label says). It was almost too fast cure when applied to the lens. I left it set a bit too long (20-30 minutes) before dressing up the seam and it was difficult to smooth out-- my fault for waiting too long. As long as you clean up the seam and smooth it out relatively soon, it should work great.

Why did you pick this product vs others?:Top quality marine adhesive just very pricey but it definitely works and you can do without it!

The 3M Marine Adhesive Sealant 4000 UV delivers excellent performance for sealing and bonding in tough outdoor conditions. Its UV resistance ensures it won’t degrade or discolor, even with prolonged sun exposure. The adhesive is flexible after curing, making it ideal for marine use and projects where durability is key. It’s easy to apply and provides a strong, lasting hold. A dependable choice for anyone needing a sealant that can withstand water, weather, and time.

Worked well and is very strong.