Marine-rated electronics have a conformal coating on their circuit boards. This coating is important because:
1. The helm locker in your AR210, if it's anything like the previous-gen's locker, will get wet whenever you rinse off the helm. (Check the rug in there for water after you clean off the boat. Also, check the bottom seam of the sloped surface just below the dash. If you need help managing the water that enters this locker, I can give you some tips.)
2. Even if you had zero water entry, that locker will experience extreme changes in humidity and temperature. For example, say you spend the afternoon out on the water, when it's close to 100°F and 100% humidity inside the locker. As you're pulling your boat home at night, the temperature drops to 60°. All the surfaces of your boat will collect a layer of condensation, especially surfaces that don't have moving air across them. Moreover, your amps will experience a bigger temperature swing as the ambient temperature falls below the dew point. (Although Class D amps run much cooler than AB ones, D amps still run warmer than ambient temperature.) This means condensation will form on and inside your amps, which will lead to corrosion because of the many dissimilar metals that make up the circuitry. The conformal coating protects the circuitry from that condensation and subsequent corrosion. Electronics without a conformal coating won't fail immediately, but they will fail over time.
3. Any electronics that you install inside the battery locker have to further handle the corrosive gases that the battery can potentially release (as well as corrosive fumes from the engine, since the locker is not sealed from the engine compartment).
Given all the tinkering you've done with your trucks, I imagine you have a good crimping tool and you use marine-rated connectors. But if you need help in this regard, please don't hesitate to holler.
