Replacement PSU for an ADSL Router

Sorry this is slightly off topic but I believe the expertise resides in this
group to assist.

The PSU of my 3com ADSL router has failed and 3com are being less than
helpful in providing a replacement under waranty. The PSU output is rated
12VDC, 1000ma. I have obtained a replacement PSU also rated as 12VDC 1000ma
and am measuring the open circuit (no load) voltage as 16.8VDC. I have
measured the open circiut voltage of the 12VDC PSU of a colleagues Belkin
router as 12.1VDC. The question is can I use the replacement PSU (open
circuit voltage 16.8VDC) without damaging the ADSL router?

I assume the voltage of this PSU will be 12VDC when on load, is this a
reasonable assumption?

I will appreciate your advice.