The older M25XP engines did not come with a way to connect an alarm for high temperature. This means that you could overheat and do serious damage unless you were constantly monitoring the temperature gauge, which is down at ankle level. This is a serious issue, which was addressed on later model Catalinas.
When I had to replace the thermostat housing, I ordered one from Catalina Direct with a second port for installing a temperature switch that can drive an alarm at the helm. While I was at it, I also bought a dual-tone alarm module to install at the helm engine panel. One connection is for the original oil pressure switch, and makes a solid tone. The other is for the new water temperature switch, and makes a pulsing sound.
After some previous rewiring, there was a spare wire running from the engine to the panel that I used for this new connection.
The engine panel did not have a location for the alarm module, so I drilled a hole with a hole saw and mounted it.
Update 6/29/23
The sound from this alarm is very shrill and loud. This is a good thing for getting your attention, but it is not very nice to listen to every time you start the engine. So I decided to reconnect the oil pressure alarm to the old buzzer. Right now, the new alarm is only connected to the coolant temp alarm sender. I plan to add and exhaust temperature alarm sender soon and will connect it to the second input at that point.
Update 7/29/23
I added an exhaust temperature alarm to connect to the second input.
