The little Yanmar engine in our J/109 is cursed with the basic panel with no gauges other than rpm and just warning lights for other parameters.
While I have taken a bunch of precautions against overheating, which I have written about before, I really wanted to be able to read engine temperature because:
- It’s good to know that the engine has reached operating temperature before increasing the rpm to full cruise.
- Conversely, on short engine runs, like just leaving the wharf to put the sails up, its good to be sure the engine has reached operating temperature before shutting it down, even if it means motoring a little further.
- Monitoring engine temperature can warn us of impending problems like a damaged water pump or partially blocked strainer well ahead of the alarm going off.
- Conversely, persistently low engine temperature, which is also bad for the engine, can warn us of a thermostat that has stuck open.
There are various ways to add a conventional temperature gauge to an engine in the absence of another threaded port, including teeing it into the water heater heat exchanger circuit, but that would mean finding a home for the gauge on deck, and cutting a hole to accommodate it.
Here’s a better and easier way: