Courtney the Dancer
Most ships run a dry exhaust, like trucks, so you would need to plumb it into a location before where the cooling water enters. Pyrometers in trucks are used to keep from overheating while pulling hills, and it's pretty dramatic how fast the temp can go up if you keep your foot on the throttle when the RPM's start dropping if you don't downshift. If you are properly propped you should never have to worry too much about it in a sailboat (especially if you don't have a turbo), your coolant temp alarm should alert you to an overheating situation before you do any damage even if you don't have a temp guage (most Yanmars ?). I could definitely see an advantage to having a Pyro in a tug boat with variable pitch prop, or any large diesel engine for that mattler.