The major problem is finding a safe, secure location to store the equipment. In my case, I'll be hauling an arranger keyboard, stand, console, seat, amp and a cart to transport the gear up the dock to the venue where I'll be performing. The equipment will likely fill half of the quarter-berth, but that's the least of the problem.
Salt air and moisture is deadly for most musical equipment, especially acoustic guitars. The only protection is the cases the gear is stored in, and of course if they are made of laminated wood, a good coating of highly polished wax should be applied after each use. My keyboard case is not air tight, which is the way it should be, but most guitar cases, especially hard cases, can be utilized to store a guitar in relative safety. The electronic gear, which is what all of my equipment consists of, is very susceptible to the marine environment and every possible precaution must be taken to prevent its untimely demise.