To disable that you can do
$spec = New-Object VMware.Vim.VirtualMachineConfigSpec
$spec.tools = New-Object VMWare.Vim.ToolsConfigInfo
$spec.tools.syncTimeWithHost = $false
Get-VM |
where{$_.ExtensionData.Config.Tools.syncTimeWithHost} |
ForEach-Object -Process {
$_.ExtensionData.ReconfigVM($spec)
}
To set the NTP configuration inside your guest OS, depends on which guest OS you are running.
You can do that part via Invoke-VMScript