are the ones that you don't use with plastics. The chemical that makes it smell is caustic to plastics and causes the plastic to degrade. I believe Life Caulk falls into that category. "The polysulfides, such as BoatLIFE's Life Calk or 3M's 101, bond to wood better than silicone does and also bond fairly well to metals and fiberglass. However, they can melt some plastics and acrylics, such as Lexan, and some vinyls can become softened by exposure to their solvents. Because of the metallic nature of sulfur, they are not particularly suited to electrical insulation and should not be used between two items of dissimilar metals". Also, if you are putting the fitting into a cored hull, instead of coating the core with epoxy prior to installing it, I would prepare the hull differently. Coating the core certainly helps but it does nothing to protect against crushing. Even plastic type fitting can crush a cored hull. It's less likely but it can happen. I would take a number 10 wood screw about two inches long and cut off the head. Then I would bend the screw just about a third of the way from the end at a 90 degree angle. Accounting for the bend, that should give you about 3/8 of an inch to the point and the rest long enough to put into an electric drill chuck. Tighten the new "tool" into the drill and put into the hole and start digging out the core. Once the core has been dug out back the 3/8 of an inch the hole will be nice, clean and neat. Make up a batch of epoxy thickened with micro balloons and fill between the inner and outer layers of the fiberglass and you're done. The hull will be solid and leak proof. I use this method with any and all hull and deck fittings on any cored boat. It takes a bit longer but it's so worth the effort in the long run that I don't even think about it. You could use harder thickeners as well but I usually have the micro balloons so I just use them.