Some thoughts on sealants. Sealants are primarily silicone, polysulfide, polyurethane and blends of them. Add to that butyl rubber.
First, as a rule, I like butyl for any hardware that has the potential to flex or move. Chainplates fit that criteria. My default sealant for most everything else except plastic is LifeSeal. For plastic I generally use silicone. Here's a reference for where to use sealants: https://drive.google.com/file/d/12WmFxRiqzUw2xiqLaEtfBpS1pYocZID-/view?usp=sharing Note that Life Calk is a polysulfide. Do not use polysulfide for plastic. LifeSeal is a blend of silicone and polyurethane. 4200 is polyurethane. I don't use 4200. Got too many partially cured tubes. Look at the expiration date before you buy. 5200 is NOT a sealant. It's an adhesive. From the 3M website: "3M™ Marine Adhesive Sealant 5200 is a one-component, high-strength, moisture-curing, gap-filling polyurethane for permanent bonding of wood, gelcoat and fiberglass." Note the word "permanent"! A bit off the subject, but Flexpaste seems to fix gouges in rubber rub rails fairly well. Who'd a thunk it? An "as seen on TV product" that actually works on a boat! -- Dennis C. Touche' 35-1 #83 Mandeville, LA
