I just installed an engine temperature gauge to replace one of the idiot lights on my Yanmar 3GM30F. I used a CruzPro T30 digital gauge with an over temerature alarm feature. The istallation was straightforward and I was able to use the blue/white sender wire from the old sensor to the pedestal. I used a Telflex 3/8" temp sensor and calibrated the gauge for that sensor. The gauge seems to work well and the engine temperature with the boat in the slip reached 153F and then leveled off. It's been too snotty to take the boat out on the bay but I did run the engine for a while at 2000 RPM. I'm wondering what is the normal operating temperature of this engine. The Yanmar manual say that the alarm signal comes on at ~202F. The water in the marina is cold this time of year.