Part 1 – Collect right marine equipment
Good specifications - better specifications mean better sound quality. For receivers, look for a high CD signal-to-noise ratio, a wide frequency response, and plenty of RMS power. If radio's your thing, check the FM sensitivity spec - the lower, the better. Speakers should fit nicely into your cabin panels, be made with UV-resistant materials, and handle plenty of power.
High power - since you'll be listening to your music out in the open, you'll want plenty of power for clean, clear sound. Most of marine receivers come with built-in 4-chanel audio output, but if you love it loud or want to drown out the nautical background noise, you might want to consider adding an external amplifier to your system.
Some details You have to take attention when choosing marine audio gear:
Water-resistant - can handle splashes and light rain, but not built to handle submersion. Levels of resistance vary by manufacturer.
UV-resistant - designed to withstand sun damage. Found on receiver faceplates, speaker cones and grilles.
Waterproof - able to be fully submerged, though depths and the amount of time underwater vary by manufacturer.
Anti-corrosion - specifically designed to resist rust and the corrosive effects of salt water. Examples of anti-corrosive features include coated circuit boards, plated connections, and a rust-resistant chassis.
Marine audio components:
Audio source - the days of the basic, one-trick CD receiver are long gone. From connections for your aux-in, USB, iPod to Bluetooth and Wi-Fi audio and video streaming, today's aftermarket components offer a wide variety of entertainment options. If you have a larger system in mind, get a receiver with more audio inputs (Bluetooth, Wi-Fi, multifunction zone control) than one auxiliary input, which will allow you to add another audio source later.
You'll want to buy a marine receiver with a coated circuit board, a water-resistant faceplate, audio outputs for speakers or external amplifier, mobile audio source dock and multi-zone controls. A weatherproof faceplate cover and a watertight remote control are great accessories to add on.
Speakers - when you're buying marine speakers, look for plastic cones and rubber surrounds for maximum weather protection, corrosion-resistant mounting hardware, and enough power to pump out tunes over wind, water, and engine noise. Be sure to look at where you're mounting the speakers — if your speakers are near your compass, they should be magnetically shielded.
Amplifiers - a quality marine amplifiers will feature coated circuit boards, plated, non-corrosive connectors, and plenty of power.
Subwoofers - bass matters on boats, too, so it's smart to invest in a sturdy, powerful marine sub. Look for plastic cones and rubber surrounds for maximum weather protection.
Speaker wire and cables - marine-rated wiring is an essential part of any marine audio system. All wires should be tinned; bare copper can corrode quickly in salt water conditions.
Power inverter - a power inverter is an incredibly handy thing to have on board. Charge up your phone battery, a laptop computer, or even a soldering iron without running miles of extension cords down to your dock. Be sure that the inverter has a Ground Fault Circuit Interrupter, which protects you against accidental shocks.
Part 2 - Placement of components on your boat
For optimum sound, you need more than just a good stereo, you need high quality marine speakers that are properly installed.
Unlike most cars and trucks, there isn't one ideal place to install audio equipment on every boat. Different models have different power and space limitations, so each installation presents a unique set of challenges. What sounds great in a sailing yacht might not even fit in a motorboat - and what's great for a motorboat might not be ideal for a sailboat.
If you're replacing your boat's existing radio and speakers, you can probably use the same mounting locations and wiring. Otherwise, you might need to cut some paneling or run new wires for the components. Select a convenient location with comfortable access to control your music and safe from salt water and sun.
It is important that your speakers can handle the power load that your stereo can produce, otherwise you run the risk of blowing your speakers. Your speakers should be able to handle more power than your stereo or amplifier can produce. Speakers are directional. When installing speakers on deck, be careful to point them toward the place your ears will be. Below deck, direction is less crucial, but not less important, since there are many reflective surfaces to contain the sound. Midrange, mid-bass speakers and tweeters can fit into side panels or the dash panel. It really depends on your boat, your needs and your tastes.
If you do not bought ultra-low magnetic field speakers – you’ll have to install within 5 feet of compasses, autopilots or other navigation gear, the magnetic flux produced by an operating speaker could affect compass readings and any other equipment interfaced with the compass.
Flush-mount speakers need air behind them. Don't choke your sound. In general, more air is better. If you have less than one cubic foot of air behind your speakers, you are at risk of inhibiting the bass response.
Custom made boxes, with calculated volume for a particular speakers are best for flush-mount speakers installation and high quality sound, but construction and installation of these boxes can be difficult.
When installing speakers on deck, it is important to consider that speakers are very directional, which means they send sound in the direction they are pointed. Be sure to point the speakers where your ears are going to be.
Amplifiers & Subwoofers
Amplifiers and subwoofers can go in a compartment under the seats, under the bow, or even on a wakeboard tower.
Grounding your electrical components can be a challenge in a boat, though some do have specific, dedicated grounding plates.
Power adapters are not waterproof, so they will need to be positioned in an area where they are out of the weather. If necessary, you can run longer wires between the stereo and the adapter in order to position them where you need them. Use solid core doorbell wire for this purpose which is perfect for low voltage outdoor situations.
Consult your manufacturer for more information on where to ground components in your boat.
Make sure that the plastic coating on the wire is intact from end to end.
Tinned marine wire is best. Since copper wire is very vulnerable to corrosion, you should seal all wires between the insulation and soldered area. Liquid electrical tape is excellent for this application.