Battery wiring

[forever young]

While reinstalling my batteries on a 1998 30 Marlin I came across a small black or dark green wire on my port most house battery. When I removed the batteries in the fall I made a diagram which shows this wire coming from a positive terminal. My question is what the heck is this wire to and does it belong on the positive terminal. The boat is all original wiring so I'm hoping someone knows the answer. This is my first year with a Grady.

 

[BobP]

Welcome ! Good handle!

It could be a bilge pump power feed to auto ckt if light gauge, like 16 AWG. You should have two seperate ones, with inline waterproof fuses nearby.

The wiring diagram for your boat is in the owners manual on the Grady website, or you can wait for others to reply, plenty of guys with your boat.
Each wire is color coded.

The wire may also be an add on by former owner, like an always on feed for radio memory circuits, galvanic isolator alarm, flowscan memory, etc.

Any such connections directly to pos battery terminals to be fused.
Waterproof fuse holder recommended for transom area.