boat sunk

[marcdups]

Got a buddy with a 5.0 mercruiser MPI that sunk on his lift, filled up with rain water above starter, fuel pump, trim motor, and completly fried all positive terminals, battery switch on the floor right next to starter on floor ( Idiots ) who ever rigged that boat was a ?????%$#@@!, know trim pump is fried, starter, fuel pump but wondering about ecm, as far as i can remember is that if you hook uo batteries the wrong way that it fries the ecm, so logic would say that it is fried, right??
BTW all the +'S were green and the metal was gone
Thanks for your input, Marc