For starter, clear out your pitot pickups with a small safety pin (or dental drill bit if you have one) and see if it works any better. As for the depth finder, I've got nothing. They don't work forever unfortunately.
Previous: 1993 Prostar 205
Red 1998 Ski Nautique, PCM GT40, 310 hp, , Acme 4 blade, Perfect Pass SG/Zbox.
Be kind. Have fun.