I used Epiphanes varnish and can't recommend it enough. It has been on now for 6 years and looks like new. I put on fifteen to 20 coats. If you go to the trouble of taking the coamings off, as far as I figure, put plenty of coats on so you are not faced with the problem of taking the coamings off for half a lifetime.
Epiphane is true spar varnish, not the poly varnish that cracks and peels off within three years - at least in the midwest. It is good stuff and I don't know if it can be beat.