Guys : Those blue multi ground connectors are CRAP!!!!! I've replaced all of mine after an episode where I turned ON the cabin lights and the bow running light came ON !!
The trailer connector plugs (Gummy Bear) are also CRAP!!!! I knew about them, but had installed a Balmar Hi - Output alternator and wired it direct (negative & positive) to the batteries. A few years later I finally decided to change out the trailer connector at the engine. After I unwrapped the 6 feet!! of black tape around the connector it fell apart in my hand!!! No amperage heat - just the engine heat slowly disintegrated it. The one behind the engine instrument panel wasn't as bad- but!!
What's so sad is that when I removed that engine 3 different times (3rd was the last) I NEVER used those connectors that were made for the production line. I just disconnected wires at the engine!!!
I've had reports of the shore power AC wire being clamped under a stanchion (underside). Another was a stern running light wire was clamped underside by a pushpit (stern pulpit) nut! That cause DC leakage which eroded the stainless rudder column at the water line!!
So as Noah mentioned, keep your eyes open when you are tracing wiring!!
And for God sake not only LOOK at the CRITICAL UPDATES, but BELIEVE them!!!! 
A few thoughts