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Old 01-17-2016, 12:20 PM   #1
City: North Charleston, SC
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Filling screw holes

I have several screw holes that I would like to fill and cover with gelcoat. Most are small, a couple are larger. One option, of course is to just put the screws back in.

My real question is, what to fill the holes with. I have read that gelcoat won't adhere well to epoxy so that's out. Is "marine filler" any different or any better than "Bondo" from the auto parts store?

I need only a small amount, probably a half a pint or so.

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Old 01-17-2016, 12:35 PM   #2
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I have used for a long time and like Marine-Tex. You can buy it in small size or larger depending on the repair.

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Old 01-17-2016, 12:57 PM   #3
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Your main worry should be water incursion

If the screw holes are penetrating the deck or anywhere that water can travel the hole should be properly sealed. To do this is a two part process. First, get a thin and very runny epoxy, like the 3m AB two part Sealer. Pour this sealer in the hole and let it run and set. Then use a thickened epoxy and fill the hole. After this you just sand and use what ever epoxy or gel coat finish you plan to use.
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Old 01-17-2016, 12:59 PM   #4
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When my rub rail was replaced, the yard filled the old screw holes under the rail with 5200, then installed the new rail over them. No repainting or gelcoat, but the 5200 seemed like a good solution to seal the holes. Not sure if it'll accept paint or gelcoat though.
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Old 01-17-2016, 02:40 PM   #5
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Westsystem makes a white additive to thicken their epoxy for bonding, filleting etc. If you are filling holes in fiberglass, mixes up a small batch of fiberglass and add the above thickening agent to get the consistency you need, then fill the holes. Gelcoat will readily stick to it as it's fiberglass. Sean did some fiberglass filleting on my boat that way and then gelcoated over it before painting it.

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Old 01-17-2016, 03:09 PM   #6
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Cabosil (sp?) mixed into gelcoat, let it set, sand it smooth, touch up with non-thickened gelcoat, sand to 1500 grit, polish with compound and if your colour match is good, the holes have disappeared forever.
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Old 01-17-2016, 04:16 PM   #7
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Originally Posted by HiDHo View Post
I have used for a long time and like Marine-Tex. You can buy it in small size or larger depending on the repair.
Can gelcoat be applied to Marine Tex and will it adhere properly?

Again, I have been told that gelcoat won't adhere to epoxy properly. Is that true or not?

These screw holes are not beneath the waterline so that is not an issue. This would be a cosmetic repair.
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Old 01-17-2016, 04:29 PM   #8
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The West System website and manuals describes how to use epoxy, then primer, then GelCote.

Usually...polyester anything right over generic epoxies tends to have a high failure rate for long term adhesion. That said...many techniques and primers between have made that old standard less "absolute".

I haven't tried Gel over MarineTex but it seems to allow overcoating of different paints and fillers better than some epoxies I have used.

I think like many things...size and shape may allow success where other repairs may fail. Just not enough data to justify blowing off the old standard just yet.

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