Yes it is normal.
Even with gel in perfect condition it isn't strange for a boat that is kept in water to add on several hundred pounds of water. I don't think this is commonly known but a good friend of mine who owns a boat factory (http://www.micore.se/) told me so. This, combined with growth is commonly the reason why the best performance numbers is found at spring. Also due to lower ambient temperature arround here.

There is protective paints that stops the water from sucking in, but I like to keep my bottom clean from paint.

In my perticular case there are also a few small patches where the gelcoat is enrirely worn through, which worsens the process. My plan for this atumn is a couple of weeks indoor with a heater under the boat to make it 100% dry, and then have my boat-builder friend re-gel the damaged areas.

I will try higher octane next time.
I ran it 60 miles yesterday and it's below half fuill now. Next weekend I will be trailing it to another Poker Run. I will keep it on low until then, and than fill it up complete with V-Power to see if I can tell a difference.

I'm spinning Bravo 30's
I've read somewhere here on OSO that 32's where stock (perhaps it was your post even), but that many switched to 30's to be able to rev them out with a bit more load. On my first tank it revved 5200-5300 but no over revving alarm. According to seller he has seen 77mph GPS.

A think that is quite likely a good day low on fuel, considering I've ran 74,8 a really hot day with full fuel and 3 persons in boat.