Thanks c_shanklin. After a little modification to get it to work the get-vmhostfirewallexception line also works. I can now set the ntp service to automatic, start it running, and enable ntp client. Here is the current script to do that.
$cred = Get-Credential
Connect-VIServer +-Server +$VCName +-Credential +$cred
Set-VMHostService +-HostService +(Get-VMHostservice +-VMHost +(Get-VMHost $VMHost) | Where-Object {$_.key -eq "ntpd"}) +-policy +"automatic"
Start-VMHostService +-HostService +(Get-VMHostservice +-VMHost +(Get-VMHost $VMHost) | Where-Object {$_.key -eq "ntpd"})
Get-VMHostFirewallException +-VMHost +(Get-VMHost $VMHost) +-name +$FWName | Set-VMHostFirewallException -enabled:$true
After the firewall line I have:
Add-VmHostNtpServer -VMHost (Get-VMHost $VMHost) -NtpServer xx.xx.xx.xx
and this fails with the affore mentioned error. I tried using vi toolkit prompt and manually entered the commands connecting directly with the ESX server. Add-vmhostntpserver still failed with the same error. Beings I am new to powershell I am unsure the meaning for pointing to pool.ntp.org. We are running ESX3.5 U2, VC 2.5 U2, Powershell v2.0, VI Toolkit v1.5. No ESXi as of yet.