My only thought is this... butyl is not an adhesive. Since the marelon fitting is just attached with a nut on the other side, the thought is maybe I needed something of an adhesive. Deck fittings that are thru-bolted, where butyl is used, are secure with their hardware by default. Just thinking that the nut holding the marelon fitting needed more help from an adhesive. I'm a fan of butyl, just not sure if this was a proper application.
Ok fair enough question.
But first -- you're saying that both a deck fitting and a cockpit drain are "nutted." So they are both both mechanically affixed, therefore adhesive is unnecessary.
Consider this - your plexi windows are held in place with a pretty stout adhesive -- Dow 795 -- which probably has more adhesion than what you might need for a mechanically-held cockpit drain. Fair enough?
Dow 795 has an adhesion of about 45 psi.
Life Seal has an adhesion of 290 psi.
Do you think that, with the mechanical bond already provided, you need a sealant that holds more than 6 times better than what holds the windows on?
Life Caulk isn't compatible with many plastics, though I doubt it would attack Marleon (glass reinforced polypropylene.
Butyl rubber isn't primarily an adhesive, but that doesn't mean it has no adhesive properties. Most car windshields used to be held by no mechanical fasteners -- only butyl rubber tape. (More and more are being affixed at the factory with polyurethane.)
See RC's admittedly unscientific test of butyl tape's "holding power" ie- a deck cleat lifted above the surface or his "knife test."
However, as one very astute member says "Your boat, your choice!"
Ken K
