Hi my name isXXXXX will assist you.
The engine has a fuse # XXXXX on the starter main connection that blows when battery is connected incorrectly. This fuse has to be replaced 90 amp fuse from Mercruiser. here is the diagram of the fuse and the part number. click here
Post back with questions.
The red wire goes to the large post.
There is nothing to go on the left post in your application. You are correct on the other.