Originally Posted by white74
also a good primer for butyl is to paint a thin coat of contact cement (use the good exterior stuff not the water based or interior stuff)
I own a CS27, smaller sister to Maine Sail's CS36T. Both boats, as well as all other CS boats were built with all through bolted deck hardware bedded with good quality butyl. The hull'deck joint was butyl bedded as well. All original deck hardware on my boat is still leak free - the issues were items installed by previous owners using silicone or other sealants. On any item I have removed, like the forward hatch I replaced, the original (35 year old!) butyl was still doing its job. The adjacent balsa was bone dry and the hatch was hard to remove.
If it needs a primer it is not good butyl.