furuno GP1670F GPS signal problem



I just installed my new GP1670 F in dash, without external antenna. First start with C-map card installed. many satellites viewed, but all in red. No fix. After trying several things including resets, same situation. Then I started it WITHOUT the C-map card, in the same position as beforeand I got a very good signal. Turned off equipment, put in card, and everything ok.
However, using the boat with the map, I find there is a displacement of map vs. real position of at least 300 meters.
I reset the unit again and from then on have not been able to obtain any fix. sometimes a couple of satellites have green columns but immediately dissapear. I tried taking the unit out and making it work on top of cockpit, thinking it might be bad GPS reception of equipment in dash, but experienced no change.
There is no way I can get a position fix!
Fishfinder works fine.
Any suggestions on the GPS reception problem?
Can the map be off-set to coincide with real position?
I am taking unit to be seen by Furuno rep.
I would start with a factory reset/default and see what happens but I am sure you dealer will get to the the bottom of it.