Electrical problems on our boat?

We have a 2004 25 pro line walkaround which has nothing to do with the problem but anyway when I hit the left trim switch the left engine shuts down and we have to switch both batteries to all position and start it or trim the engine we replaced the batteries and the voltage is running at 14.1 to 14.7 when running which is normal I got some advice that the connections are corroded and one anode connection was but I don't know if that's the entire problem. Also when I turn on any accesory the trim gauge stops working and the fuel gauge gives a false reading. I hate making starting our boat up a 3 minute process in stead of just turning the key so help me out here.