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My two cents. OSI has been a very good caulk for the 30 + years I have used stuff like this. I never saw it sold as marine caulk nor was quad sold as such. Quad is a very sticky, flexabile, strong caulk used extensively by siding contractors for vinyl [where it will not be painted] and for wood where paint may be necessary. I would use silicone if I thought the deck ect. may have to come up in a two year time frame as it is very easy to remove cleanly. If I were not planning to remove the caulked item for a long time and really cared about the color that much, I would not hesitate to use quad.