Why add an amplifier to your boat?
It is extremely crucial to add an amplifier to your boat stereo mainly because of the environment. When trying to create good sound in an open environment, Power is one of the most important factors. A lot of customers try to run their stereo loud with only marine headunits which don't have a lot of power. This creates distortion and thus damage the speakers. A marine amplifier in a boat solves this issue.
Location of the Amplifier
When purchasing a marine amplifier, you need to consider where you want the amplifier to be installed. Are you able to install it close to your battery? This will determine the length of your cables. Are you able to mount it where water won't get to it? This will dictate how weather proof you amplifier need to be. Is it going to be mounted where it's easier accessible? This will determine if you need to tune it before mounting it.
Consider the power you need to match with your speakers as well as the number of channels you need to power all your speakers. It is always good to have a little more power than required for the speakers, especially in a boat application because it is open air which means good power is a necessity. Depending on the number of speakers, choosing an amplifier to power them all sometimes can be a diffucult task.