The following article explains how to delete a course off a V2 watch. Courses cannot be deleted from a V3 or G3.
It is not necessary to delete a course from the V2 watch as the watch has sufficient memory to hold a large number of courses. However, if you do wish to do this, carry out the following instructions:
Mobile - iOS and Android
1) On your mobile app navigate to the "Find Courses" screen.
2) Search for the course you wish to delete.
3) Untick the tick box next to that course name.
Now following your next course sync that course will be deleted off of your V2 watch.