I installed the Aqualarm raw water alarm last spring and there was
some discussion here. I had some calibration issues and finally
decided that it should be treated as a water flow stoppage alarm and
couldn’t be used to warn of diminished flow. The manufacturer
confirmed that this was the case, at least with a small engine
operating near the bottom of the calibration range.

There were some responses that "real" sailors checked the exhaust
water flow every two or three minutes and didn’t depend on gadgets. I
began to wonder myself is the unit was just one of those enthusiasms
you have when outfitting a new boat. (My very basic panel doesn’t have
water temp gauges or even room for them.)

I was hunkered down in the cockpit yesterday grimly motoring into 25
mph wind and chop on the way to get the boat hauled for the winter
when the beeping started. I checked the water pump and it was hot.
There is no way I could have seen the water flow under the counter in
those conditions. The Aqualarm certainly saved me from an overheat
event.

I finished the trip under sail. The strainer was clear, the impeller
looked good, I’ll have them figure it out when they winterize the
engine.

Full story he

http://home.maine.rr.com/rlma/Boat20.htm#Latest

--
Roger Long