Taking engine's temperature - Yanmar 3GM30F

[bsangs]

Quick question. When using a laser, non-contact thermometer, which is the best area of the engine to measure to get an "accurate" temperature reading? I'd like to make sure I'm measuring it correctly, since I only have a warning light on the control panel, and don't have a temperature gauge. Thought it would be easy enough to find with a Google search, but I'm coming up empty. Thanks.

 

[Jerry VB]

Free advice from a random person on the internet. Discount it as appropriate.

There will be a temperature sensor screwed into/on the engine block somewhere. That is where you want to measure to see if your temperature gauge is reading accurately. (Typically there is an oil pressure sensor and a temperature sensor - both will have one, possibly two, sensor wires attached. Measure both if you cannot determine which is which. I would expect both to be similar).

However, I would not look for one temperature reading. I would take multiple readings...

• Targeting the cylinder heads (shoot at the injector bases if you can) - look for roughly equal temperatures. If one cylinder is significantly hotter or colder than the other two there is something going on that probably isn't good.
• Target the water jacket around the exhaust manifold - it will get warmer as you go from the fore end to the aft end of the engine. The hotter end should not be excessively hot; well under 200 degrees F.
• Target the heat exchanger - it will be cool where the cooling water from the raw water pump enters and warmer where the water exits and is injected into the cooling elbow / exhaust stream. Again, it should be well under 200 degrees. (IIRC, the raw cooling water goes on the outside of the heat exchanger.)
• Where the cooling thermostat is mounted, typically close to the cooling water pump. This should be about the temperature of the thermostat, typically 160-180 degrees.