This invention provides a means for automatically adjusting the volume of a marine audio device based upon the vessels engine(s) speed, or RPM. An engine speed, or RPM, input signal is processed such that the volume of the aforementioned device is increased or decreased as said signal changes. This is particularly useful when the volume of an audio device such as a radio or CD player, should be loud enough to hear when the vessel is under power but quiet enough for the user(s) to enjoy when the vessel is at rest.