I would buy either a marine battery with threaded posts. Or buy the lead clamps that have the threaded posts and use those. How do you have those other cables terminated?
What do the other set of large cables go to. You can't put a ring terminal on the clamp bolt like that. Since they don't sit flat you get a bad connection.
The Suzuki is an excellent motor. Problem is Suzuki has not kept up with parts supply. No aftermarket support for them. The aftermarket is taking up a lot of slack for the OMC motors. Nothing for Suzukis that old. That Suzuki is as obsolete as my McCulloch 75 hp.