Spider cracks in deck
 

I have a lot of spider cracks in my deck and I'm going to paint the deck this year, do you think that would fix the problem ?

Anytime I painted a crack, thats what i ended up with, a painted crack. Probably something like destroyer used, one of the "Bedliner" type products would do a better job. I've got a 13 whaler with gelcoat crazing all over it. I painted it with a 2 part rustoleum that covered well and wears tough. But you can still see the cracks. It's a crab/scallop boat, so no big deal.

The cracks are usually just the gel coat. You have to widen the cracks and taper them out, then use a filler/resin. I would probably use epoxy and lightweight filler in that case.
You could use pre-made polyester filler(Bondo).
I have used both in different places with success.

If you are using a textured paint, you could maybe use one thin layer of glass cloth. You should use primer before paint.

So if I just paint with deck paint you think the spider cracks would come back ?

yes

The way to really do it is use a Dremel tool and grind them out and fill with epoxy then you can paint it and it should be fine

I did it exactly the way Mj explained it and I worked just fine,

I was trying to do it the easy way , just plant but it looks like I have to grind out the cracks But I have a lot of them so it will take some time but if that's the way to do it right then that's what I will have to do

mawshj
 

there used to be a product that had a wetting agent in filler that would creep into the cracks and self level. I was told that it worked well. I can't recall it name but I will try to find it.I think defender marine sold it