In this photo I am reading the temp of the raw water circuit on it's way out of the HX.
The raw water path on my Westerbeke engine is as follows; Raw water pump to HX intake, HX outlet to transmission cooler inlet, transmission cooler outlet to siphon break, siphon break to exhaust elbow.
Please IGNORE the temp readings on my Raytek Infrared as I did not have the time to properly warm up my engine. I already had these numbers recorded and merely wanted to photograph how to get your engine temp baseline.