At home, I cover my boat. But when transporting on trips or in the water, I have wondered if the sun will eventually fade the colors of my boat or cause it’s structure to degrade. I was amazed at how the sun apparently turned the hatches on one of my boats (uncovered back then) to dust after a few years. I’m most interested in composite boats as that’s what I own. Does gelcoat have UV inhibitors built in? I have wondered if there is some sort of compound that you should apply once or twice a season to promote one’s boat’s longevity. I wouldn’t want to apply something that would, in turn, get into the water and cause any ecological harm.
Not necessarily, it depends what the manufacturer of your boat actually used.
Gelcoat is essentially opaque, so it provides UV protection for the underlying structural materials. It’s considered to be a sacrificial layer and UV will fade and damage it over time. Generally, the more vivid the color, the worse it fades. Polishing and waxing it will reduce fading, but the key thing to to keep it out of the sun when you’re not paddling.
I wouldn’t be too concerned about polluting the water, as waxes aren’t water soluble; otherwise they wouldn’t work on a boat or any other vehicle.
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Gelcoat will last a long time, but does benefit from a good coat of wax occasionally. I buff and wax my composite kayaks once a year (they are stored inside but used regularly).
My 25 year old sailboat’s gelcoat still will buff back to a nice shine. It’s due for it again, but Florida is not kind in the UV department.
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Per the instructions for my Epic:
Protecting your kayak from harmful UV rays will keep it sound and looking its best for many years. There are a number of products available that work well. 303 Protectant and UV Tech are two examples that may be sprayed on the boat then wiped down with a rag. This simple process protects, and restores shine. You only need to do this 3‐4 times a year.
Elsewhere it specifically mentions applying 303 to the hatch seals, which are black flexible foam rubber.
The deck is covered with dried water spots from the hard water that I paddle in, so really I am applying 303 to calcium carbonate.
The Materials Safety Data Sheet for 303 says it has a pH of 9.8 so, as you said, it will not dissolve calcium carbonate residue. If it’s a problem, a gentle wipe-down with a weak acid (ie vinegar) should dissolve any carbonate, then you can apply 303 to the hull instead of over the hard water spots.
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The gelcoat from Epic is a very UV resistant polyester and not considered to be a “sacrificial layer” 
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Kayaks can degrade more from how they are stored than during use. That is because they spend a lot more time being stored that being used.
I 303 after I get back from kayaking because I get a lot of light reflection even though I have a roof over my kayaks. The 303 also stays stuck a little better if it has time to cure.
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The problem with 303 is that it’s water soluble; it just washes off.
Never had that problem. It is designed for marine use. You re probably applying too much and not thoroughly rubbing it in.
UV exposure is UV exposure, whether in storage or in use. I use 303 but there are many marine waxes that also feature UV protection.
Many paints are water based and still hold up in the water. It is because the polymers in it harden as the water evaporates out.
With 303 I saw a lot less pollution sheen around the boat when I let it cure for a few days.
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That doesn’t change the fact that it’s water soluble. It doesn’t “cure” like paint, it just dries as the water in it evaporates. There’s a big difference between “water-borne” products like latex paint and “water-based” products that remain water soluble after they dry. It’s too much to get into here, but you can look it up online. You can’t “rub it in” on gelcoat, and rubber or closed-cell foam hatch covers aren’t going to absorb it to any significant degree. It’s just going to make them look pretty temporarily. If you’re seeing any “pollution sheen” on the water, that tells you that it’s washing off.
Don’t take my word for it; put some on your boat, let it dry, then try to wash it off. See for yourself.
It’s completely worthless on hulls, but if you paddle flat water and your deck rarely gets wet, you’ll get some benefit while out there. In conditions where your deck is getting soaked, it will provide some protection until it’s washed off, but unless you reapply it frequently, it’s not going to do much, long-term. If you have to store your boat in the sun, applying it after you get off the water will help to protect it, but even if it doesn’t get wet, it doesn’t last indefinitely.
If you want reasonably durable protection, waxing is your best bet. Perhaps one of the ceramic coatings that are all the rage now would be the ticket, but I don’t know if they’re compatible with gelcoat, as they’re designed to be applied over paint. Or you can do like I do and just skip it, with the knowledge that you’ll need to buff the deck every 5 years or so if you want it to look pretty.
From the 303 ® website: Treated material must be protected from rain/dew until completely cured. CURING: 12-24 hours dependent on temperature .
They can call it whatever they want, but it still washes off. Like I said, try it for yourself.
I’m no chemist but Google says typical gelcoats are UV-resistant. Brodie’s boat looks like proof.
I’ve seen posts before asking about the importance of UV protection when transporting but I have never seen a post about significant UV damage from normal use. It’s always from long term outdoor storage.
Wenonah recommends “any automotive cleaner/wax” once a year. Hemlock recommends 303 monthly. Some folks on this site have recommended Turtle Wax Ceramic Spray because it’s so easy…just spray on wet boat. In my experience both wax and 303 wear/wash off but neither washes off instantly. I’m happy to let others debate which products last longest.
I think you’ll be fine if you do nothing but if you want a little extra protection I’d use 303 or Turtle Wax ceramic or 3M Marine cleaner/wax if you don’t mind the extra work.
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I use this product sold by Current Designs on my glass boat. Produces a nice shine but I have no idea whether it really helps with long-term protection. I figure it can’t hurt.
SPF-50 Boat Guard
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Has anyone tried the 303 product with wax added? Company claims it lasts 90 days.
$12 @ Bezos’ Bazaar.
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I use turtle wax hybrid ceramic. probably gone on hull after a trip or two. Last on the deck of my Boston Whaler boat for 5-6 weeks. Literally 3 minute job to spray hull top and bottom and wipe even when slightly wet. i spray everything ans it leaves no white on deck lines like a wax. Beads water much longer than 303. Turtle wax ceramic wash is good. Soft brush long handle it’s 5 minutes max. so after paddling for 2 hr or 8 hr I can spare the time to take 8-10 minutes on my kayak. Even blast my Seals deck bag material and it beads up water like my deck lines.
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I like that.
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Yes, especially frequent use.
303 protectant works for inflatables and many kinds of surfaces.
High UV resistant varnish for over wood and epoxy.