It tends to be a lot more expensive to keep a boat in FL than most places.
Most marinas charge by the month rather than then the season. Down here you will pay anywhere from $14/ft/mo up to around $26/ft/mo, more in the winter, depending on amenities. Some marinas will give you summer rates all year if you sign a year lease.
Also, a lot of the marinas are fixed dock rather than floating docks.
Most marinas here also charge for electric. The electric is metered and usually have a minimum of around $30-$50/mo.
You will also need a diving service to clean your running gear and bottom. This should be done every two weeks in summer and once a month in winter. This runs about $1.75-$2.25/ft. Most marinas will not let you do your own diving. I think it is an insurance issue, or so I am told.
As for insurance, expect to pay at least double what you are now. If you are in a marina that is classified as a "Hurricane Hole" some insurance companies may charge a little less. That is also another issue. If there is a named storm, some marinas ask you to leave. Then you need to find a place to either haul you or that is a hurricane hole.
There are a lot of dry rack storage marinas, but most don't take anything over 30'.
