My two year old neoprene spray skirt is leaking. Can I waterproof it and what is best to use.
no treatment
as far as I know your problem must be more about fit or tears and not the inherent waterproofness. Maybe the rim elastic is over stretched or you have a cut. Or is it just leaking through the tunnel in which case wearing a paddle jacket over the tunnel may help.
Two step process
1) buy a new sprayskirt and put it on top of the leaky skirt
2) remove the old skirt
really, no treatment?
I have a new neoprene/nylon tunnel skirt that leaks too. Water pools onto the neoprene (I use a Greenland Paddle), but it’s the “breathable” nylon tunnel part that gets soaked and then soaks me. I tried spraying it with that general camping water proofing spray, but I guess it only works for shedding water - not if it’s submerged…
was just talking about neoprene part. NM
possibly a DWP treatment
I had some luck with a DWP fabric treatment on the fabric covering of a neo sprayskirt, and good luck on old neo hatch covers. I think it was one of the Nixwax products.
I would guess that on a two year old skirt that the leaksource is at a stitch or glue joint, or damage as others have mentioned. If you had some left over DWP treatment laying around I guess it wouldn’t hurt to try.
If no damage has occurred, then the
most likely site of damage is one of the seams. The seam where the tunnel is sewn to the deck of the skirt is a possibility.
I would suggest getting the product Seam Grip. Mount your skirt on the cockpit, inside out (under surface facing up), and paint or squirt Seam Grip onto the seam, all the way around. Let it dry while the skirt is still on the boat. Seam Grip penetrates very well, and when it dries, it is very flexible. Some will recommend Aquaseal instead, but it is the same thing (a flexible urethane) in a less penetrating form. Aquaseal is good for small cuts in neoprene.
If this does not do the job, or if you are feeling fanatic, you can mount the skirt on the cockpit normal side up and paint Seam Grip on the “up” side.
If thus treating the seams does not work, then you may have hidden damage in the neoprene deck, under the Nylon facing, so that you can’t see it. Look for areas where the Nylon facing seems slightly loose. You can paint these thoroughly with Seam Grip. Again, it is best to do this with the skirt in the “stretched” position, on the cockpit. Any more obvious bite in the neoprene can be fixed with Aquaseal.
Seam Grip and Aquaseal both tend to harden in the tube so that you can’t get the cap off to use the rest. That’s OK, just trim a corner off the bottom of the tube and squirt the product out there.
I don’t think there is a fix
there was an earlier discussion of this problem: http://www.paddling.net/message/showThread.html?fid=advice&tid=1172523
Seems like the GP is the culprit. People who don’t use one don’t think neoprene leaks, we who do use Gp"s know better. 
I have found that a dry suit is the only way to keep my okole dry.