I'm with you Tom. I wouldn't expect to need the water choke unless it was cold but...
If you get it all set up nice and the thing works perfectly when the heat is needed, what happens when you turn the heat off? The choke will eventually cool and you are stuck with a "permanently" choked engine or stuck having to run the heat all the time (and the pesky thermostat will be shutting it down anyway...).
I say get yourself a manual choke kit for it as I can't think of a good way to hook up the water without having to either have a second valve (for a by-pass system) or suffer inconsistant operation (for an in-line system).

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Mike!