Is there really a difference between the 3M 5200 and a good quality silicone you buy at the home building stores?<br /><br />I use my boat only in fresh water
Yes... 5200 is a urethane which has adhesive properties that far surpass that of any silicone.. <br /><br />Think I'm kidding? Glue two pieces of fiberglass together with 5200, then after 5200 has cured, try to get the pieces apart.. <br /><br />Is 5200 always necessary? Nope... If you're just sealing thru-hull fittings on a trailered freshwater boat, 5200 is overkill... Good silicone would be fine..
It's all about longevity. If you use 5200 below the waterline you find it will last much longer than silicone. Stay away from silicone if it will come into contact with gasoline. 5200 is far more resilient that silicone. It is a pain in the gluteals to clean 5200 off your hands. My personal philosophy is if it's hard to clean from your hands, it's probably a better product.
and just so you know, there are 2 types of 5200... "fast cure" cures in about 24 hours, the regular type takes something like a week. Suppossed to be the same in the end.