4x4Chipper

In the units setup I found the GPS set to "NAD27 Alaska" in Map Datum. I toggled down to and set it for "NAD27 CONUS" assuming it was for the continental US. I have no idea if any of this will effect the accuracy of the unit. i still get readings that are 80' to 130' off of two other GPS units that more or less match each other. Of the settings that are user-selectable, which ones will effect the accuracy? How can I get this thing narrowed down a little closer to dead-on? Is there a benchmark anywhere that can be used? Or assuming that the other two units used are close, how do I dial mine in to get a similar reading? Help!

I just bought an eTrex HCx on ebay. The former owner lived in Alaska. My son and I went geocaching with the unit yesterday and were unable to find the first cache. A clue provided online was found over 160' away from where we zeroed. Despite this we were still unable to find the cache. On our second cache of the day, I zeroed on a group of trees 255' away from the actual cache (my son found it by accident when he got bored and started wandering. A third cache was not found; it was indicated to be on a rocky formation, and the GPS continually indicated it was over 90' away in some deep woods. Following the failure to find the first cache, I toggled through the menu and found the WAAS was not enabled. I enabled it and kept the unit on until we reached the second cache location (about ten minutes). We spent approximately a 1/2 hour in the area, and as stated, the cache was 255' from the stated position. This morning I discovered the unit was set for the incorrect time zone. I'm not certain if this caused the disparity. My old blue legend always got me within a few feet of a cache. I will have to borrow it back from the new owner and see if the readings compare. Any thoughts? Is it possible the unit is set up incorrectly? Is there anything I can do with the unit to make the accuracy a little closer than a couple hundred feet?