Could be on the radio question, it really shouldn't be on the ignition circuit at all. It should be on the accessory circuit with the bilge pump, blower, lights, etc. The only thing on the engine circuit should be the engine.
If you don't have power to the engine plug, you don't have power to the instruments or your radio.
I just uploaded this wiring diagram for your engine. It may help
http://www.4shared.com/document/vLDe3zXz/Wiring_Diagram_30L.html
Also go up to the Adults only sticky and download oem service manual #26
Those two should help you understand where the power comes and goes. Tomorrow, I have to go to work................... as a Boat Mechanic no less