Join Date: Jul 2008
Location: Dickinson, Tx. / Somerville, TX
The first coat could be thinned but spraying is not normally recommended with urethane. And why are you asking about the first coat in specific?
I have done a lot of boat work in my life as well as lived and traveled on my own boat and I agree 100% with Steve about Epifanes. That is all I use.
There is a 2 component urethane for outdoors but last time I checked, several years ago, it was about $150/qt. Great stuff and is very temperature sensitive for application.
As for MinWax Spar Varnish, it is a joke. It shouldn't even be allowed to be sold with a name like Spar Varnish. I doubt it would last more than 2 months in direct sunlight during the summer in the south.
Retired woodworker, amongst other things, Sold full time cruising boat and now full time cruising in RV. Currently in Somerville, Tx