Y wrote:
I see what appear to be small crack marks on my hull. Is that common?

On a 13 year old boat it's certainly not *un* common.

What you describe sounds like gelcoat cracks (surface layer of
fiberglass). Most likely they don't leak. You don't say whether or not
these cracks are in a spiderweb pattern, that is fairly common. Also
it's common for cracks to radiate from a corner. This can be due to
flexing of the fiberglass structure (gelcoat is stiffer & more brittle
than fiberglass) or it could be due to thermal stress.

Gelcoat cracks are quite easy to fix, if you can paint a surface you can
fix them yourself. You have to carefully grind away a small amount of
the gelcoat in the cracked area, mix some new gelcoat, and spread it on
smoothly.

OTOH when you grind away some of the gelcoat in the cracked area, if the
crack gets bigger instead of smaller as you grind, and it looks like it
goes all the way through, then you have a bigger problem. It can still
be fixed fairly easily but it's going to need structural fiberglass cloth.

Fair Skies
Doug King