As part of our efforts to get better indications of engine issues, we installed a new thermostat housing with a port for an overheat alarm. We also added a dual alarm module, which produces the sound for the overheat. But we wanted to get an early warning if we had issues with the raw water cooling, so I added a temperature limit sensor to the exhaust hose and connected it to the second input on the alarm module.
There are two general ways to add the exhaust sensor. One involves drilling a hole in the exhaust hose and inserting a probe. This would provide the most immediate indication of a change in temperature, but all the ones I found are meant to send to a gauge. Since I wanted something that would alert me, without having to constantly monitor the gauges near my feet, this was not ideal. The other option involves a band that you put around the outside of the hose, and acts as a switch when it reaches a certain temperature. This would work nicely with the existing alarm module, but it is unclear how fast the hose temperature will rise if raw water fails.
Since I wanted an alarm, rather than a gauge, I went with the band switch option. There are a bunch of them on the market that trigger at 200 degF, but only Borel Manufacturing has one that triggers at 165. Since the hose is rated at 200, I wanted to go with the 165 version, so I would be notified well before there was a failure at the hose. Their band is part of a combo that includes the alarm panel. This would be good if you don’t have an existing alarm with an empty input. I contacted them via email and was able to buy the band separately and installed it the next weekend.
I tried to test it by heating up the hose with a heat gun, but I was not able to get the heat distributed enough to get it to trigger. The area where I could aim the heat gun got up to 180+ before I turned it off, but the area where the sensor is only got to 140. I guess I will just have to trust that it will trigger if the hose gets hot from a raw water failure.
