Nothing against Lowrance, but we have a Garmin 440s model GPS chartplotter with the optional sounder unit. Its nice to have the sounder readout on the same screen as the GPS unit, as it reduces clutter & is easier to read when mounted to the binnacle of the wheel right in front of you. Some sailors mount their units on a swinging arm that can be swung into the cabin when not in use. To me this is a lil' bulky, & its harder to read & impossible to hit reset or program buttons without a helper or leaving the helm seat position. The Garmin has been around for a few years & is pretty reliable & can be had for under $400. Check around online as they are on sale all the time. Garmin are pretty much the leader in GPS technology these days, but don't expect them to support your unit with parts for more then a 10 year period, which seems to be about the life of most marine electronics these days. Ray Marine are the best, but the most expensive may be a bit over board for what your needs are in a fresh water lake. At least you guys don't have to worry about the tides, but the Garmin also comes with good built in tides tables, all US coastal water maps, fuel & destination info, etc. As the above post noted, the hardest part is in wiring it up to the binnacle & remember to wire in fuses, if it is not wired to a breaker at your panel. A dedicated breaker panel circuit is a good idea.