If the radio is lighting up, the panel fuse is good. If you have an aftermarket radio however, it may not have a fuse on the panel and instead wired directly to the battery.
First thing to check is the back of the radio itself, if it has multiple fuses then it may have one for the speakers.
Make sure the volume is up and you have the correct source selected (i.e. Aux input setting with no aux input will result in no sound). If you have just two speakers, someone could have set fade or balance incorrectly.
If you have an external amp, that is likely culprit; either loose wires or blown amp.
Also check the speakers with a multimeter. Is any voltage going to the speakers with the radio on and playing?
2006 Bayliner BR205
A1 Gen 2 1.47
5.0 carb engine