Universal primer/paint?

[Copacabana]

I want to repaint some of the inside of my boat (painted fiberglass inside the cabin). I have no idea what paint was used previously. Is there a kind of primer or paint I can apply over it that won't react with the old paint? The current paint isn't chipping or peeling, it's just a bit yellow. I was hoping not to remove it all before painting...
Thanks in advance!

[Suijin]

The best primer to use is the one recommended by the manufacturer of the paint you're going to apply.

Prep is king when it comes to ensure a good paint job and that the new paint adheres for it's service life. Make sure you abrade the existing paint until it's uniformly (that means ALL over) dull, then wash, then clean with whatever the paint manufacturer recommends. Denatured alcohol is a good bet.

[Copacabana]

Originally Posted by Suijin

The best primer to use is the one recommended by the manufacturer of the paint you're going to apply.

Prep is king when it comes to ensure a good paint job and that the new paint adheres for it's service life. Make sure you abrade the existing paint until it's uniformly (that means ALL over) dull, then wash, then clean with whatever the paint manufacturer recommends. Denatured alcohol is a good bet.

Thanks. I'm just concerned the new paint will react with the (unknown) old paint. Is there a paint that can be applied over all other paints?

[Cheechako]

For decades Shellac has been the "universal separation barrier" for painting if you are concerned about bleeding thru, or sealing the surface. But as long as you dont have ltex or some huge mistake like that, I would just try a hidden area with some new paint and see how it does after prepping. Shellac dries in minutes.

[Copacabana]

Originally Posted by Cheechako

For decades Shellac has been the "universal separation barrier" for painting if you are concerned about bleeding thru, or sealing the surface. But as long as you dont have ltex or some huge mistake like that, I would just try a hidden area with some new paint and see how it does after prepping. Shellac dries in minutes.

I suspect it might be latex...

[Glenn.Brooks]

Scrape off a bit of the old paint to find out what it is. So,long as it is NOT latex, most modern marine primers will cover and adhere just fine.

You can also use acetone to clean and reduce the surface in preparation for priming. Personally, I would never use shellac as a first coat over old fiberglass. Modern marine primers are specifically formulated to bond well with existing paints. And they will adhere much longer and stronger than shellac. You will need a prime coat anyway, so why put an extra layer between the existing finish and your new finish??

[Copacabana]

I'm just wondering if a latex primer and a coat of latex would react to the old paint. I'd actually prefer to use latex for the final coat (easy to apply and repaint in the future). It's not a large area and doesn't get any abrasion. Would a latex primer work over PU (if that's what is in fact there now)? The fact that the paint has yellowed seems to indicate (to me, anyway) that it's not PU. The current paint is almost a matte finish (or perhaps a semi-gloss that has lost some of its gloss).

[jkindredpdx]

I've used both Kilz and Interlux Bilgecote successfully. You could try one on a small section and see how it reacts.

BTW. I usually wash the area with TSP before painting.