Originally Posted by ShinyShoe
You'll find very few people who would say that Sika Flex 291/292 is not the dogs danglies. There are a few suggested alternatives which some say are just as good. 3M 5300 I think and Tec 7.
Most importantly the advice on here is always that standard silicone is not suitable.
(FYI Sika 292 will be pretty much permanent so don't be planning to unscrew any time soon!) The 3M and Tec 7 may be equiv to 291 or 292 I'm not 100% sure as not used them...
3M 5200 is pretty much considered permanent. For a mounting bolt; it's not like 5200 will make the bolt permanent - tools will still break the bond (but don't count on picking any remaining adhesive out of the holes...)
If you want a less aggressive sealant, move to the 3M 4200 line.
Both are polyurethane sealant/adhesives, pretty similar to the Sika line of PU adhesive/sealants.
Another option is epoxy or fiberglass resin (which is also epoxy, I think.)
BTW, if you're sealing the transom, ideally you want to coat the drilled holes' interior, not just goop the stuff around the bolt/screw head.
And as Shiny Shoe stated, bathroom silicone sealant is not going to cut it - it breaks down with water and US exposure.