The source of this text is the (former) forum of GPS-Expert.nl

Upgrade your basemap to a more detailed routable World map

The zūmo has 2 maps when it leaves the factory:

Base map Europe or America, not routable
Detailed map City Navigator, routable

The base map gives you some details on your continent. But if you look on another continent, you will see nothing.
With the Garmin product World Wide Maps you can have more details in these other regions, but still not routable and the information is not much either.

Solution is known longer for other type of Garmin GPS units. I have tried the solution on my zūmo GPS and it works perfectly.

Step 0:

If you don't have a Garmin map product on your PC then skip step 1. MapSource should be installed on your PC in step 1!

Step 1 (install Worldmap under Mapsource):

Download the file SetupWWBMap3.zip (22 MB), created by mister Elsinga. This is the product Garmin World Routable basemap v3
Extract the zip file. In there is an executable, click it twice to execute the file SetupWWBMap3.exe
Choose for English and complete the installation
Start now your MapSource program and in the upper left corner you can choose between different Garmin maps which are on your PC (if you had previously 1 map than the choose menu is now available)

Map selection

Now you have the routable World Base map in your Mapsource and you can make routes. (Map will fail if you zoom out above 3000km!)

Step 2 (download basemap from Garmin):

Download the iQue 3600 World-Wide Basemap (25 MB)

Find the file, but not to double click to install! With the right mouse button Extract to

Copy the file GMAPBMAP.IMG from this Zip file to a folder on your PC.

Step 3 (install basemap to zūmo):

Connect your zūmo to your PC
Make a backup of the file gmapbmap.img which is in the X:\Garmin folder at your zūmo.
Delete the file gmapbmap.sum (the zūmo will create this by itself again. just a check for file integrity)
Copy your download and extracted GMAPBMAP.IMG to your zūmo in to the folder GARMIN:\Garmin
Disconnect your zūmo from your PC and let it start up.
Check if you see roads at Miami, Capetown, Sydney, Amsterdam (zoom out, move and zoom in).

Testing:

Make a route in your PC with Mapsource at the World routable Base map and download it to your PC. If it all went ok, you have completed your upgrade.

My zūmo now in Sydney, Los Angels and Miami:

Test 2

A route somewhat experimental through South America:

Test 4

You have now MapSource and a zūmo with:

Base map World, routable!
Detailed map USA version 8NT, routable.