Get the company names of marine electronic manufacturers (radar, gps, communications gear etc..). email their customer service reps and ask the same question. Try emailing Denon, Yamaha, et al, they may have marine rated gear. Most marine electronics are totally sealed from everything. Even if you get decent marine rated gear, you'll still have problems with your speakers - marine rated speakers are crap, basically designed for underwater use. Suggest you buy cheap and plan on replacing them often.