How do I waterproof a Sunbrella boat cover?

[John Blazy]

I bought two grades of Sunbrella when I upholstered my boat - thinner for the seats and a thicker version (awning grade) for the canopy / cover. I assumed that the thicker stuff would cause water to bead off, which it seemed to do 12 years ago. Every time I go through a rain storm trailering the boat, it sheds most of the water, but alot soaks through.

Anyone have any idea if the waterproofing agent has simply weathered off, or if I was supposed to treat it with something?

I suppose I could go to the Sunbrella website and scour it for recommended products, but wondering of Thompsons Water Seal would work.

[Mel Fulks]

Years ago there were always waterproofing treatment formulas in the magazines. There are now products sold for that but I have not tried any.

[Roger Nair]

I would google the subject, feel somewhat informed, then then call Sailrite for tech advice and products.

[Kev Williams]

I don't think Sunbrella uses a waterproofer, it just naturally is waterproof. After a few years, the weave starts to expand, letting water thru...

The "accepted" waterproofer for Sunbrella is 303 Fabricguard- Some swear by it, some say it doesn't work all that great. It can get expensive too.

Not sure you'd want to put Thompsons on it because of the mineral spirits in it. Not sure what else is in it, MSDS doesn't say--

What I use is NOT recommended by Sunbrella, but I've found no problem with it whatsoever:
343388
I get it at Walmart, $5-something a can I think, it does work pretty good, lasts 1 or 2 years depending on the weather it's exposed to, about the same as any others.

A basic 8' x 8' or so bimini will take a couple of cans...

[Mel Fulks]

Sunbrella is 100 percent acrylic, I think it probably does have some kind of treatment. It is dyed before being woven ,possible that the treatment is in the dye.

[John Blazy]

Thanks a ton for the tips! Will try the watergaurd stuff