I have used this pump for the last >15 years to pump hot water in my home brewery. It isn't quiet (but there are ways to mitigate that), but it works with hot water, runs on 12 VDC, and is reliable. In the brewery it runs continuously for a couple of hours at a time, with and without water flow.
http://www.grainger.com/Grainger/DAYTON-Marine-Pump-1P811?Pid=searchWhen using a pump like this, be sure to throttle the flow on the outflow of the pump. Do not starve the pump, it will cavitate, become very noisy, and will burn out.
This pump isn't self-priming, so it has to be located below the supply tank, but that's not a big deal.
<Chas>