I'm looking for advise on how long I need to let the final coat of epoxy cure before starting to varnish...
What are you working on David, I thought you were way past that?
Until now, I've been running the boat with a couple of coats of epoxy - I sanded those pretty aggressively with 120, then added another coat. I'm just not sure if I can wait 24-48 hours and then add a coat of varnish over the fresh epoxy, or if I have to wait longer.
I seem to remember something about 7 days,of course pending on temp.
You'll want it to be completely hard,you can tell by sanding with fine grit if it gums up the paper its not ready.
In my experience David as long as you are using west 207 or system three silver tip you should be fine already. I have only had issues with blushing hardeners that seem to need several days.