Originally Posted by TRBenj
RTV silicone has no business below the water line of a boat! Sheesh.
5200 is what I'd choose... not sure why you'd want to do this job again in the future? 5200 would be a PITA to remove if you did, but thats because its good at what it does (sealing below the waterline). If absolutely necessary, it could be undone though.
3M 4200 or Boat Life Caulk are 2 other slightly less permanent options.
I would have to disagree on the use of RTV below the waterline in that application. Especially the location of use and the draft these boat have. But I will agree polyurethane and poly sulfides are better sealants.