2 map sets on one memory card - How to change between them [Garmin 176C]

Looks like this was it (it is not always obvious what mapsource is doing);

Not sure but it sounds like you might be only selecting segments from one mapping product in Mapsource on the PC.

In MapSource I select the first mapping product (say WorldMap) then select the segments I want. These will show up in 'Maps' on the left, then I change the top box to the second product (say Metroguide) and select the segments I want from this product. All segments from both products are listed in the 'Map' list with the total number of map segments and the size at the bottom.

I then upload them all at once to the GPSr.

In my GPS V at the map screen I hitMapsource infowhich gives me a list of all segments from both products.
I can toogle up and down and de-select individual segments.

If I hitagain I get options; Enable all, Disable all, Enable Australian Metroguide v4.00, Enable World Map. I can toogle up and down and hittingselects that option.
It works a bit backwards as after I first load 2 products, all segments from both products are enabled (and it just depends on which has the higher priority as to which is displayed).
If I select Enable World Map, it disables Metroguide (all segments).

The Metroguide/Bluechart behaviour should be identical.

Afterwards, in Mapsource on the PC if you select 'Open from GPS' and only select 'Maps' it will download segment information (not all the segments, just info about them) and display which segments you have loaded and you can change map products to confirm you have segments from both products loaded.

BurnieM came through again. Works the way I thought it would now and I can stop loading up everytime I swap between car and boat. The explanation provided was easy to follow and worked first time.

Thanks