Yanmar coolant temp fine but engine running a little hot

[stepbnd]

I had a pre-purchase survey done and the surveyor said the Yanmar 3HM35F was running a little hotter than usual. He checked the temperatures in several places using an infrared temperature gun. The exhaust hose temp just below the elbow, oil pan, oil filter, and injectors all were about 15-20 degrees hotter than what he said they should be, but the coolant temperature checked at the thermostat was normal (about 140F if I recall). The injectors were about 160F - all three were about the same, I think the oil temp at the pan was about 185F and the exhaust hose just below the elbow was about 118F. Can't remember the exact temps - mainly that everything but the coolant was 15-20 degrees too high.

The surveyor seemed to think it was an indication that maybe the exhaust elbow was beginning to clog.

Any ideas about what would explain the engine and exhaust temps to be high but the coolant temp to be normal?

[olepedersen]

anything from a bad raw water impeller, to obstruction in heat exchanger. but 185degrees is a normal operating temp Ole

[djmarchand]

If the engine ran at wot in gear for 5 minutes and didn't trip the overheat alarm, then it is ok. The alarm goes off at 200 or so degrees.

David

[stepbnd]

Yeah, the alarm never went off, but isn't the sensor for the alarm on the thermostat housing? If so, that area stayed around 140F.