1999 F50 Shorted Battery How Do We Go Thru And Fix It

Hello All,
We shorted the battery on a 40 hour used Yam 50TLRX, Whats the best way to trouble shoot and fix this correctly. Thanks Bob.

[boats.net]

If you just hooked battery cables up backwards then it probably blew the fuse on engine, replace fuse and should be ok.