The biggest difference is the thickness each product will build. That is to say, if the boat is fair and smooth now it doesn't make much difference. If the boat is not fair and smooth, and you want it to look like a mirror then there is a bigger difference in what you can do with boat products vs automotive products.
Automotive products are also much, much faster to work with. Look at the recoat windows. With awlgrip, you spray today and sand tomorrow. Some automotive products you spray today, sand in 3 hours, fix whatever issues you seen, spray again and topcoat over the primer wet on wet.
Car primers build in 1-3 mil thicknesses.
Awlgrip has a few that are good for 60 mils wet.
is good for 20 mils.
If you don't have an epoxy
built boat, fair it:
and 3M High Strength filler with a dab of EverCoat 407 ultra smooth glazing putty here and there.
2. Or use fiberglass
, resin, and gelcoat.
In either event my favorite primer in all the world is Awlgrip 545. You can topcoat with awlgrip, or shoot PPG twin pack paint over the top. JAU is the name of PPG's single
stage color coat that doesn't require a clear coat. It's full name is: Direct Gloss Acrylic
It is clear coat, that gets a color pack mixed into it. It sprays like a clear coat, which means it comes out of the gun almost a mist... It is thinner than Awlgrip and builds slower than Awlgrip, which is saying something to anyone that has sprayed it. Awlgrip sprays like milk. PPG sprays like cooking
Neither are what you would call, overly easy to spray. Temperature matters, humidity matters (If dew falls, they don't shine) as does the mixing technique and how much thinner is put into each batch. You need a dryer on the airlines, as condensed water
blown out with the paint makes bubbles. You need a big enough compressor
to keep and hold the pressure so you get the same results every time you squeeze the trigger.
It also helps to have a decent gun that atomizes fairly well at a steady pressure. Cheap guns
can spray thin products well, but the flow rate goes to the moon and you have to move your body, not just your hand fast enough to apply an even coat.
It goes with out saying, that spraying awlgrip topcoats and isocyanate paints is bad for you. It'll make your children
be born naked, and you should respect the products as they can kill you. They really should not be sprayed without an air supplied respirator, as a carbon cartridge respirator is still slow suicide (after 15 minutes, you are soaking in the isocyanates... as is spraying without a full suit and goggles.
primers is bad enough. Atomized epoxy hardens up in your lungs, never to come back out. Folks don't last very long around these products if they don't protect themselves... and even then exposure is still to some of the most free radical chemicals you can choose to expose yourself.