Question about Old Electrical Components

I am trying to diagnose a starting issue, engines barely / not cranking. Reviewing electrical setup, see pictures attached. I will clean up all the connections but components are old so maybe it's time to replace? In particular I am wondering about the green ribbon component, seen in close up. Is this some kind of vintage fuse? Should it be updated? If so with what? (it is wired in line with a 250amp fuse). Just replaced old 0/4 cables to the starter motors. Batteries are only 2-3 years old, doing full load testing this weekend.

Thanks

Ryan