Probably not going to be a good choice.
Frequency is too far off. You really do need a frequency specific antenna when doing this sort of stuff. While some can be tuned, you're going to be much better off with the right tool for the job.
Not sure where your repeater is going, but if it's going at an established site on a leased tower, you may get some pushback from the tower owner. Amateur radio grade antennas are often not welcome.
Antenna gain isn't always your best friend, especially if you are going to be on a high mountain top.
Lower gain antennas or antennas with a downtilt will help coverage a lot more than additional gain will.
I'd avoid taking advice from anyone who'd recommend an amateur radio grade antenna for a GMRS repeater. It may seem like a cheap option with a lot of gain, but it's not going to work out as well as an appropriate antenna that is designed for this sort of application.