This is going to be a rant about 3M Marine Adhesive Sealant 5200 and why you shouldn't use it on your boat. If you are not a boat builder, you have no reason to use it. The problem is that 5200 creates a permanent bond between two surfaces. There is that word "permanent". What, exactly, is permanent on a boat? Is a port-light permanent? Or a winch? How about combing? A stanchion? A bow roller? None of these are permanent. All of them will need to be serviced and replaced at some point. It might be 10 years, or it might be 20. If you use 5200, you, or the person who eventually owns your boat, will swear at that idiot who used 5200.
Okay, there are a few reasons to use 5200. If you are putting a new thru-hull below the waterline, that might be a reason. I think we used 5200 to fasten down the mast step on our Catalina 22 that was loose because that has a seriously long lever trying to pry it up from the deck. But almost anything that you think you should 5200 for could also be done with 4200 or even 4000.
Some people will use debonding agents, or have a scheme with a guitar E string for getting 5200 separated. But why do that when you could have used 4200.
Captain Boomies did a cool demo on why 5200 is the wrong product for anything you can think of on a boat. When you think of something that you might want to use 5200 on, ask yourself "can I use 4200 or even 4000 for that thing".
