In pursuing my little battery issue... (too many connections right at the batteries and loose connections) I discovered the wiring for this battery monitor, but it doesn't appear to be telling me anything. I can't find anything about it on the web. So I am highly inclined to just remove it and toss it. I also removed wiring for a solar charger which is not there. And I labeled wiring at the battery area so I know what is what.

Currently I have both batteries back into the boat, all connections tight and either battery able to start the engine. And I bought only test equipment. (which of course can be used on any other projects too... tools are always good investments)