I'm with RC & Rhouse.
I put myself through college doing auto electronic upgrades. Best sound systems were always "matted" to stop the metal popping noises and hear the music. Fast forward to today and working in car manufacturing we apply a liquid sound deadener that cures like dymamat or other brands. Night and day difference.

I have kilamat in my amazon cart right now but waiting since it is 20* in Ohio. My plan was the firewall, interior engine side panels, Trans cover, fuel tank cover (floor), and back of the sub panel under the dash. Next will be the surf pipe and hoping we can finally talk while pulling someone. Every boat I have had has been an I/O and you have to yell regardless of what you are doing.