NASA EXHAUST TEMPERATURE MONITOR
It is common practice to inject cooling water into marine engine exhaust systems. This cooling reduces the exhaust gas temperature to a level where rubber and polymer exhaust components can be used.
Such "wet exhaust" systems perform reliably and have a good life expectancy as long as the cooling water is always present. A failure of cooling water, even for a short period, can lead to catastrophic damage of the exhaust system components which, in turn, can lead to fires, leaks of toxic gasses and reduced exhaust life expectancy.
A cooling water failure can be caused by a temporary blockage of the raw water inlet by a plastic bag or other debris or it could result from a burst pipe or poorly performing water pump. Either way an engine temperature gauge will not give adequate warning. The temperature of the engine block, full of water, will rise very slowly whilst the exhaust gas temperature will rise from a few tens of degrees centigrade to a few hundred degrees centigrade in a matter of seconds.
To give advanced warning of cooling water problems, either restrictions or complete failure, requires an exhaust temperature sensor. Some sensors measure the temperature of the outside of the exhaust hose. Unfortunately, as rubber exhaust hoses conduct heat very poorly, by the time a warning is given the internal temperature may have already exceeded the manufactures recommended maximum. A further problem with such a device is that the user has no way of knowing if it will actually work when needed.
The NASA Marine EX-1 measures the exhaust gas temperature directly and displays it in degrees centigrade or Fahrenheit. Once the normal working temperature has been established a maximum temperature, a few degrees higher, can be programmed into the EX-1 which will then sound an alarm if that temperature is exceeded. Even a small rise in temperature can indicate a potential problem such as a minor blockage, leak or failing pump which can be corrected before a complete failure occurs.