I'm wondering if you might not have an alarm go off everytime you are at idle or just putting in the water, since water pressure at those times are next to nothing.
Why not just use the high temp alarm setup?

I figure if I can get an alarm before the engine gets too hot, it would be a safer thing all the way around. I've lost two impellers over the years and each time, the black exhaust sections of hose seem to get so hot it appears as though black particles are being exhausted.... I'm hoping the black smoke is just from the exhaust hose and not the engine itself...

Just extra precaution I guess....

As for really low pressure, well that's something I'm trying to understand to see if a setup like this will really work and so far doesn't look like it will cost too much....

call fred @ trick

I can get it for you at a great price call me!!!!

Looking at the Gaffrig gauge, doesn't look like the water pressure goes higher than 15psi....??

Goodt - do you carry complete gauge packages? My intentions are to totally redo my dash this winter.

and lazer cut dashes also

Mr Anderson..... you mentioned connecting in the water tube to the intake manifold. I've got 454mag carbs... where do I connect it in at? I see that behind the carb and to the starboard on a high point of the intake manifold there is a bolt that looks like access to a passageway, is this the water passage to pick off from? I prefer to connect in on the intake manifold rather than the side block drains since I hear a lot of complaints of dirt clogging the water tube.

Thanks!

We've fitted exhaust temp alarms to both big and small block motors, they sense when the exhaust runs dry and fires off an audible alarm.

The sensor fits in the top of the exhaust bend for a through the prop install, or in the diverter for switchables.

I ran a water line off the block and I have to watch that the line does not get clogged up. I use a sender isolator to keep the sand out of the sending unit for the guage and the low pressure switch. I had the low pressure switch connected to the audible alarm and a warning light in the dash. As someone said earlier, the pressure is low at idle and sets of the alarm so I disconnected the audible alarm and kept the warning light. I wouldn't hear the alarm while running anyway.

It's easy to tell if the line get s clogged up. The pressure does not change as rapidly.

East Coast,
Check this link out I think you will find exactly what you want.

After turning on the ignition switch, the detector waits 45 seconds to allow engine start. Several times per second the sensor measures the density of surrounding fluid within the fitting. Normally this will be raw cooling water. In the event of cooling water failure, the water drains and replaced with air. The sensor detects a drop in density and the alarm relay is activated. The relay can be connected to existing alarm(s) or our Alarm Annunciatior Panel (Part # ALN). NOTE: Our wet exhaust high temperature sensor (Part # EXS) can be connected in parallel with the flow detector for extra measure of safety. Both loss of raw cooling water or high wet exhaust temperature will sound the alarm. Requires only one input on alarm panel.

http://www.borelmfg.com/products_wf_detect.htm