Can heat cause cracks in gel?
 

I layed the boat up on the trailer a little over 2 years ago with the engine removed. I keep it here at my house and have a good cover on it. Today I pulled the cover to replace it and give the boat a good cleaning to get it ready for sale and noticed the first gel cracks on it that I am 100 percent sure were not here when I layed it up.

Is it possible for the Texas heat to crack gel?

I know, never assume anything!!!!
 

Assuming you are talking more about surface crazing rather than cracks, heat and age are the two most common causes. I have seen newer boats do it; likely from the mix being even slightly too hot when applied.

Stress (twist, flex, bowing) will also cause crazing.

There are a few products which protect and hide this crazing, but it is still there, just not as noticeable.

I likely need to clarify something here, it is not really heat as much as extreme. Cold will accelerate the aging process too.

Fibreglas has a life expectancy like everything else and the lay-up lasts much longer than the surface.

Some of the restorers I know are using more and more paints than gel when resurfacing. There are applications where they prefer gel, but as a very general statement they are going to the two part paints for ease of preparation, application, clean-up, mixing and endurance. Fibreglas is constantly improving, but the paint seems to be as, or more, durable, easier to match in a repair and more fade resistant.

Sometimes true cracking can be extreme crazing!

I friend rebuilt a transom. The curves and "joints" on the transom significantly cracking. Long story short, they were a result of the wood core being all but rotted out.

Thanks, the cracks or crazing is just under the fairing where he black meets the white and the cracks are in the white. The other spot is is again black on white. These are the only spots on he boat. I know it's 21 years old but it had no gel crack when I layed it up so could not figure it out.