Disconnect the positive wire from the alternator away from the ammeter. Then take this wire and hook it up to the positive on the house battery. Standard practices require you to fuse the wire at the house battery. Look up and see what wire size you have coming off of the alternator and use the amp rating of that wire at engine
room temp BoatUS BoatTECH Guides: Choosing Cables & Terminals for Marine Service
. For instance, #8 wire can only handle 68 amps inside engine room. So you would like to fuse this wire at the battery at 68 amps. If you cannot find a 68 amp fuse, most likely, fuse it at the closest value that is under 68. If your alternator puts out more than 68 amps then you will need increase the wire size. I know, this is cumbersome but this is the safest approach and will prevent headaches in the futre.
As far as the echo goes, it is a good system. Just remember to mount the echo in a cool and dry location. I have seen many of them destroyed within a year because of excess heat and moisture. Make sure you hook up the echo with the house wire going to the house battery and the start wire going to the engine battery. If you hook it in reverse your echo will pull amps out of the start battery and try and charge your house battery. NOT GOOD. You also want to properly fuse both red wires at each battery. Trust me, this is recomended and it is the safest approach.
About the ammeter, it really is not a good idea to run your alternator through an ammeter because if that ammeter goes then your alternator goes. This is a good chance.
If you ask about why fuse the wires. This is prevent a catastrophic fire. Yes, if the fuse for the alternator blows out then you will loose charging abilities but you will prevent a damaging fire caused by excessive amperage through an underated wire.
RECAP: Look at your alterantors amperage. Make sure the wire you have on there can support it at engine room temp (link provided). Fuse the wire correctly at battery. Hook up echo correctly in good location.