Minwax 63051 Helmsman Semi Gloss Spar Urethane, 1 Quart by Minwax

Q: Can this product be applied to painted surfaces.

I have used it over wood carvings painted with acrylic paints and have have excellent results in an outdoor evironment.

Q: can i apply the oil based urethane over a water based paint to protect it?

You can but this is why you should use a water based poly over the oil poly Oil based poly has an amber hue, whereas water based poly is clear. An oil based polyurethane will continue to amber and darken over time, while water based poly will remain clear for the lifetime of the hardwood floor. ... Water based poly dries much faster, and several coats (up to 4) can be applied in one day. This explains why fritz the cat who did answer this question as well is why theirs yellowed

Q: How is the viscocity out of the can, is it more like warm syrup or more like water...or somewhere in between? Thank you!

Maybe Slightly Thinner than warm Syrup, So probably between Warm Syrup & Water. A word of advice though, I had an extremely difficult time working with this product & had to sand and reapply many coats to get a satisfactory finish. It dries fast & if you run a brush over it after is has sat more than a minute it will create rough brush marks. Additionally if you apply more than a very thin layer it will crack similar to a crackle pattern. Unless you are putting this over a pure white background I would recommend that you use the standard "Crystal Clear" non-water based urethane. It has only a light yellow tint and is much easier to work with in my experience.

Q: Can this product be applied over an exterior wood stain?

In fact it can, but being unfamiliar with the product, I purchase it thinking that it's use would result in a shine. I learned that "spar" must mean something other than gloss or high gloss. I then purchased the "Minwax Gloss aerosol which gave me the desired result, although several coats were required.