Jeff,
Well as Loren will tell you, this group should be a great source of info as you get to learn your new Ericson and its systems. You can usually get an answer to just about any question within hours - especially if you ask it during the week when many of us are at our desks at work and would rather be sailing!
If you look in the photo that Loren posted, the water heater is the rectangular block just to the right of center. Do resist the temptation to ever stand on that block, as it is not built to take the strain. On the front of the heater are the connections for water in and out, along with the pressure relief valve, and the 110 V connections. Just forward of the water heater, underneath the plywood floor, is going to be your starboard water tank. Next to the tank is the muffler. All the water forward in the lazarette is the holding tank, but you probably found that by now.
Usually are 3 batteries, underneath the starboard settee. The main water tank is athwartships under the port settee. An optional water tank may be found forward under the V berth. What else is hard to find..... The main bilge pump is under the galley sink mounted on the bulkhead next to the ice box. Next to it is the strainer for the bilge pump. There won't be a raw water strainer or accumulator tank under the sink unless a previous owner added them. The pump and strainer for the shower sump are mounted inside the engine compartment, on the bulkhead shared with the head, along side the electric fuel pump.
The engine is reliable and easy to use, but do take the time to locate the bleeder valve on starboard forward near the oil filter in case you have to bleed the engine, and the decompression valve. Get to know the engine zinc, which will be on the underside of the raw water heat exchanger (a 6: diameter tube about 16" long) on port at the aft end of the engine.
Be sure to get to know your steering gear too. There is a panel on the overhead in the aft cabin underneath the pedestal that comes out with a dozen screws. That panel gives you access to the steering cables for maintainance.
And on and on...... Welcome to the group, and best of luck with your new boat!