Enamel or urethane?

[JimCt]

Anyone know of a reliable way of determining if a painted surface was done with enamel or urethane?  Sometime in the dark past the interior of my 240 was painted.  The two-part primer I want to use calls out specifically that it must not be applied over enamel.  I've sanded most of the paint off but there are some areas, inside three-way corners for instance, that would be difficult to get to.

[John Jones]

Try wiping the paint with lacquer thinner or acetone or MEK.  The reason they say that is the two-part paints use really hot thinners like MEK and such.  If applied over enamel, even years later, the enamel will bubble up and turn loose.  If it will not wipe off with a strong thinner, you should be ok.  I might still try to test a small spot by making a tiny bottle cap size mix of the new paint and put a little over the old paint.  You will know within a few minutes usually.

[JimCt]

Thanks... will try the test J.J.  Sanding the paint that's on there, it seems like urethane or epoxy but guessing isn't good enough considering the work involved if I'm wrong.

[LilRichard]

I agree that you need to know for sure... although I highly doubt someone shot your boat with enamel... I have never seen that used in a marine environment.

However I have never seen a lot of things done that I found on my boat  

[JimCt]

If it was sprayed, I'd agree, but it was applied with a brush.  Not a horrible job but not a good one either. Number of areas where he didn't bother to sand the gelcoat.