See full version: 3m marine sealant 5200 vs 4200
Pull the part off and make sure to clean the area where the 4200 will sit between the part and the deck. Now the trick is, apply a liberal amount of 4200 on the bottom of the part and install it with the supplied screws or bolts BUT don’t tighten is down hard. Make sure it has a tiny bit of play, but that you have full contact adhesion with the 4200.
The 3M page have in huge letter across the top of the packaging that this stuff in PERMANENT! If you use 5200, you need to plan on never taking that piece off ever again. In most cases when you try to pull apart pieces bonded with 5200, the material you bonded to (fiberglass, wood, etc.) will structurally fail before the 5200 does. This will make you life so much harder if you need to work on something sealed with 5200. here
On 3M’s website, they give you some clues:
As far as the best application method for 4200: [links]
For anyone who has ever installed a piece of hardware on a sailboat or powerboat, you know the first thing you grab for is a tube of either 3M 4200 or 3M 5200. The purpose of this material is to provide a sealant against moisture and in some cases, using the adhesion properties to help strengthen the connection between parts. But do you know which one to use?
The big advantage of 5200 is it works below the waterline and has excellent resistance to salt water. If you have parts that live under water and you don’t want to worry about them working loose, 5200 is your answer. here
How long till I could launch
I should have added that I replaced one myself this spring. I used 4200. The boat has been in the water for 1.5 month, no leak, no problem. here
4200 is 300psi tensile strength and 5200 is 700psi tensile strength. 5200 is more than double the strength of 4200!
The object is paintable after applying
Here are some benefits of this sealant that make it entirely distinguishable from the other two sealants. [links]
Compared to 3m 4000, you can apply this sealant on a Gelcoat. However, wood, metal, fiberglass, and plastic are common applications. here
3m 4000 is a Polyether caulk. here
3M 4000 is supposed to be as strong as 5200 so I would not use it either. more
Meaning it kicks faster and forms a stronger bond than 4200. It is comparable to 5200 in adhesion. [links]