Volvo 260 D4 Blows Starting Circuit when turn key to start HELP

[seadog101]

I have a volvo penta 260 D4 and when I turn the key, the starter does not operate and the starting circuit blows something? and then all power is lost to helm and everywhere until it sits over night. The next day when I turn key on the helm has power but when I turn to start something blows and no power. Can you help me diagnose where my problem lies.

Thankyou

Seadog101