I want to pull my bow rails and reseal them.
My question is would 3M 4000 or 4200 be better to use. Or is there something better?


Thanks for any help in advance

Either of those will be just fine. You are just wanting sealing, not the bonding that you would get from 5200. A nice bead around the base and threads, install and snug the bolts. Don't crank down on them, you'll crack the gel and pull the glass down distorting it.

I use 3M Marine silicone when needing a water proof flexible seal where a gap needs filled, such as around port windows.
For my railing reseal, I used 4200.

I pulled my bow rails to get them powdercoated and I put them back on using the 3m marine. So far they look pretty good. That was about 4 months ago. I trust most 3m products.