Re: Launch Time after thru-hull replace
DrB, the spec sheet for Sikaflex 291 claims you should wait one full week prior to immersion in water. Google "sikaflex 291, datasheet" and you'll find a PDF file to open. I suspect there would be no problem waiting less than a week, but perhaps the people at Sika can give you some telephone or email support in this regard.
Perhaps 3M 4200 doesn't have the one-week waiting period, but I've only used Sika products so I can't say.