Vikingstaff
Moderator
Lots of secondary thinking along these lines too these past few days. The dealership service department people (prior to seeing the boat and when I went up and spoke in person the next morning) immediately started wondering some of the same things, particularly theorizing about a dead short somewhere. They were thinking that seems a likely hypothesis initially given the speedy and intense damage that would have needed a large current draw.Sorry to see this but glad it wasn't worse in terms of damage or human casualties. You were fortunate to have caught it right there and somehow had the presence of mind to document it live.
I'd be curious to know the root cause when they figure it out. I've spent many hours working on the battery and charging systems in our boat, which has 6 batteries(!), so I know a lot can go wrong. My eyeballs tell me that was a dead short somewhere, like a pinched hot wire to the frame ground or something like that. The only other big current draws are going to be the power steering pump, sea legs, or maybe if you had a mondo stereo. The first principle of ABYC wiring standards is that each wire coming from any battery MUST be fused as close to the battery as possible (~2' or less), with the correct size fuse to protect that wire gauge. It has little to do with what is connected, rather to protect the wire itself from heating as happened here. This looks like that protection failed or was somehow shorted over. I'd look very closely at the SeaLegs electrical installation myself since it was aftermarket - wire size, location of fuse/breaker, etc.
In my thinking post incident, the other portion you mentioned that resonates so much with me is that the protections failed or shorted over. Seems like it should have been “contained” to rear wiring between Perko Switch, fuses, etc… However, wires frying is all past those points. How and why? That is what has me and the service department circling back to some sort of short somewhere along one of the wires that finally made contact and set this all off? And of course we have this phantom draw down that was maybe happening with old batteries, but for sure happening with the new ones. What’s up with that? That shouldn’t have been happening with Perko Switch off. Thus, is the failure somehow with the switch, and if so, is that behind what happened?
Goodness….too much speculation and rethinking/overthinking. I cannot stop rethinking things trying to figure it out. Ugh!
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