I can't answer for how your boat is wired but mine is set up with two positive connections on the battery. One (4awg) powers the motor and leads straight to it. The other ring is crimped with 3-4 wires leading back to the helm. This bundle includes the accessories power (switches and depth finder), gauge cluster power (speedo), and ignition/trim power <--- pulling from memory.
If the house connection were loose on your battery terminal, effecting your gauges and trim, you more than likely would lose all power at the helm(e.g., depth finder). If the main positive wire going to the engine were loose, you'd have lost engine power before your gauges quit or likely at the same time.
That's why I reccomend testing your trim. If it works, one or more of your wires connecting to the ring on the positive terminal have come loose or an in-line fuse has blown (my personal opinion based on your description). If it doesn't work, you know you need to check the battery connection of the larger power wire. If it still doesnt work, then go to dealer, because a fuse has probably blown somewhere.