silicone

I think I saw a post at some point stating that Lexel will bond to silicone. But the manufacturer says no. The problem is that silicone's surface energy is very low, I the same range as Teflon. Nothing Dheres well to it.

There is a product called Sil-poxy which is meant to bond tin or platinum cured mold making silicones. But your typical big box silicone is acetic acid so I doubt it would work.

I'd stick to just removing the old silicone, it's not worth the aggravation if/when your new sealant just peals right off.