Calling all Spider Crack Detectives

Hello Friends,

Noob question here:

I am currently “restoring” a 70s fiberglass Mohawk. In some areas there are spider cracks visible. As stated above, I am a total noob and I can’t tell if the paint on it is above gelcoat/is gelcoat, whatever. After watching some videos regarding gelcoat spider crack repair, I’m pretty sure I can fix it, no problem. However, if it’s not gel coat, would I be able to shave down these cracks and fill them with gelcoat until smooth, or should I use some other fiberglass filler? I’m including a photo of some of the cracks; I’m not sure whether it will be helpful or not vis-à-vis the advice you’d be able or provide.

I apologize if these questions have incredibly obvious answers; there’s just too much conflicting info out there on YouTube and I’m facing a case of choice paralysis.

Thanks in advance,


Looks like weathered and cracked gel coat. Gel coat is a polyester material that provides a bit of abrasion protection to the hull and protects the resin from UV degradation. But it adds no strength and is largely there because it looks nice, or did look nice.

In my opinion having the entire hull re-gel coated would involve more trouble and expense than the boat is probably worth. If it were mine I would start by giving it a good cleaning then wet sanding the entire hull starting with around 400 grit paper and working down to 1500 grit or 2000 grit. You could also try a marine or automotive rubbing compound.

After that apply one or two coats of a low viscosity “penetrating epoxy” such as System Three Clear Coat. Then cover with a couple coats of a decent marine varnish to provide UV protection. Alternatively, you could paint the hull after the penetrating epoxy.


Thanks so much for your response. I was planning on repainting the whole thing (it’s not very pretty). So, would you do the sanding/penetrating epoxying before or after structural repairs (there have been quite of few of those as well). Again, thanks for replying; I’m always amazed at how willing people are to share their knowledge in this forum, and at how quickly they do so!

If the structural repairs involve external patches you must first sand off or otherwise remove the gel coat until you clearly see fibers of the underlying structural fabric, whatever that may be, in order to get a good bond.

Do any structural repairs first. Then sand smooth. The penetrating epoxy is to go into the spider cracks and other surface imperfections so that they will be less apparent after painting.

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Paint with , 2 part interlux yacht paint after sanding an fairing imperfections with the epoxy.

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We’ve had good luck with this cheapo Rust Oleum marine paint.
Using it on boats to picnic tables. Color choices are a little limited…

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Thanks so much. Have a great summer!

I have interlux on a kayak ten plus years. Yellow faded a bit but it just looks like a paler yellow. Still shinny as hell. Very tough coating.