Plexiform wrote:

... The battery tender is no longer functioning, and when I try
to start the boat it gives me no sounds at all. The clicking of the starter is
not even there. Again when I try to jump it with my car, there is no
juice...no starter clicking....nothing. ...

I'd start by replacing the battery (I had one short out - same symptoms)
and cleaning all of the cable connections.
Good luck
Howard