1986 Sleekcraft Intruder electrical issue - self inflicted pain - please help

[jamesangus]

I accidentally connected a battery with wrong cables + - , fried main cables (not paying attention/dark) and a 20 amp fuse I located on main panel by instrument cluster. Replaced both batteries, cables, battery switch, fuse. Engine cranks, bilge, blower, etc work, no power to outdrive trim and have not attempted to start engine other than briefly crank. I believe the alt is also smoked due to reverse polarity, ordering one, I have checked all the obvious areas for inline fuses, where do I start to track down the no outdrive trim power? Boat is Volvo powered AQ260 with Penta 280 outdrive. Will I need to overhaul the wiring system?
Thanks ahead of time.