I have a HD which has been partitioned. One partition runs OS X 10.6.8 while another partition runs Yosemite. When I'm running 10.6.8 the Select Startup Disk System Preference does not show the 10.10 partition and I'm forced to select the disk and re

I have a HD which has been partitioned. One partition runs OS X 10.6.8 while another partition runs Yosemite. When I'm running 10.6.8 the Select Startup Disk System Preference does not show the 10.10 partition and I'm forced to select the disk and re-install Yosemite, a very long and tedious process. For what its worrth, I don't particularly care for Yosemite primarily because the program I use most frequently, Quicken, has been upgraded to run under Yosemite and I greatly dislike the user interface that Intuit has migrated to. When I'm running the Yosemite partition, I can restart from the other partition.