If you're planning to dock for 4 months, you'll need an ablative bottom paint formulated for your waters. Imron is not rated for submersion use. Gel coat will absorb water and blister- eventually the fiberglass underneath will absorb moisture and the hull will be ruined.
I found this;
http://www.fpu-coatings.com./
this is what Dragon is using- they have a submersion-rated paint that is flourinated. That's a fancy word for a process that allows the paint to be full of Teflon but still stick to your hull. They claim it is self-cleaning. They have a bunch of US Navy vessels they've painted as well as giant fuel storage tanks so it must be good stuff. Very informative website