From MaineSails excellent series on through hulls . . .
"So why do I use Sikaflex sealants or bedding compounds rather than 3M products? That's an easy one for me to answer. In my experience I've found it less aggressive in it's adhering properties than 5200, something I really like for future
repairs. I've had vast amounts of experience, over 30+ years, with many
marine sealants and have really grown to like the Sikaflex products.
If there is one thing I've learned, in 30+ years of
boating, it's that NOTHING on a
boat is permanent, not even a
keel joint, so there is absolutely NO need for a sealant as permanent as 5200. In my opinion 3M 5200 was invented to ensure future boatyard revenue but remember what my opinion is worth.
I've seen 5200 destroy
gelcoat, port lights, hatches and
teak among other things. There is only one product not allowed on my
boat and it's 3M 5200. 3M 4200 was a move in the right direction, being less
adhesive than 5200, but for many projects it's highly
adhesive properties are still not necessary and it's still overly tenacious in it's grip.*
Now don't get me wrong I'm not saying, in any way, that Sikaflex comes apart like butter, it does not, but it comes apart easier 5200. Try Sikaflex 291 & you'll like it's adhesion, flexibility and long life."
http://www.pbase.com/mainecruising/r...ruhulls&page=2