[Cliff_Haskins]

Did you check behind the battery switch for fuseholders?

[Mbaumy]

Yes I did, all ok. Have power to the out of the switch past the fuses but no power to the circuit breakers. I feel like there's a junction block I can't see. Found the large wiring harness in the cabin and only have power to known working circuits. Can't see where the harness comes from disappears behind cabin wall.

[Cliff_Haskins]

Wires on isolator are not backwards? (Think of it as a large diode). If two crank batteries, there should be three wires... one in, two out. Also, what size boat, guess I missed that somewhere. Deep cycles usually run cabin power. As for the problem at hand - could be a bad ground, pin pushed out, chopped harness, etc..

[180diablo]

Originally Posted by Mbaumy

Yes I did, all ok. Have power to the out of the switch past the fuses but no power to the circuit breakers. I feel like there's a junction block I can't see. Found the large wiring harness in the cabin and only have power to known working circuits. Can't see where the harness comes from disappears behind cabin wall.

Hmmm, then what lies before that circuit breaker in question?

Honestly, I can't see why the boat designers would bury a junction block where it wasn't easily accessible. As Cliff mentioned above, it could be just a bad wire.... somewhere.