Need to restart VM?

I need to make a setting change to each VM.

VM Settings > Resources > Memory > Resource Allocation > Check Unlimited. Its a long story but I need to make this change to all VMs. 

First, do I need to restart the VM guest OS in order for this setting to take effect?  Is there a way to to use VMware PowerCLI to turn this flag up on all VMs at once?

Thanks