lol "marine grade" anything can hurt the wallet and is often misleading. Usually the reference is to West Systems Epoxies which is used in all sortsa projects. While it's indeed good stuff, I find it a bit pricey and I'm not fond of how it tools (or doesn't actually heh) It's
extremely hard and thus somewhat brittle as it's got little to no flex - but that doesn't matter for this application;
WEST SYSTEM Epoxy
I really do prefer the slightly more versatile MAS epoxies, all in all it's just as good (somewhat better for some things) as West Systems but it's significantly easier to tool and best yet - costs less
MAS Epoxies
BTW - a lil tip with hardeners, you'll note there is "slow" and "fast" hardeners... don't be fooled as even the "fast" should really cure overnight before tooling or use. It's mostly for reducing kick time between successive coats and doesn't really mean it
cures faster. With that in mind I usually get the "slow" hardener as it gives me more workable time before the pot kicks off and so I have less of a sloppy mess.
(kick = the epoxy isn't actually hardened but has become unusable, "cure" is fully set and finished)