Boat wont start no power?

i just bought a 86 star craft Marine, with a chevy 3.0 inboard. when we went to pick it up they had it started, but stated that it needed a starter solenoid, but it was running. got it home and changed the solenoid, now the boat will not start, the gages will not even come on, got an arc from the solenoid so the battery is working, i need help.