Overflowing kayatank

[scwafish]

Andy, I wonder if our batteries can really put out enough juice to fry the circuits of a functioning device

YES. The AGM batteries we use are 12v...the same as a car battery, just less storage. They pack more than enough mojo to ruin your day.

I guess that's my question, is the fuse there to protect the device in case the circuit fails, or is it there to protect the boat in case the device or circuit fails?

Both.