Because multiple devices are affected, I suspect that CW correctly diagnosed the problem. Unless you have a bad wiring harness with multiple shorts, I don't think you will find bad fuses. Look for a loose wire(s) or loose braided cable connections connected to metal parts. Many vehicles nowadays do not have electrical connectivity between the battery or main vehicle ground and devices, separate ground conductors need to be used. Wooden and fiberglass boats have the same situation.
__________________
|