Ofcourse you don't leave the monitor on for a long while. Just boot the game up enough to see if it lives, and then shut it off. The HV-unit of your monitor isn't the part taking excess load due to the erratic synk anyway. Don't worry. I've done this a few times.
Level42: Have you any had any destructive results doing this? Or have you only heard that it is possible to damage the monitor inputting a 25k sync to a 15k monitor?
The Sega sys24 has a few nice games. Bonanza Bros is the nicest one, but also Crackdown and Gain Ground, as is the classic Hot Rod. You have the disc drive controller too?