engine temps

[gettinthere]

I use a laser heat gun to monitor various spots on my diesel engine. At cruise rpms, oil filter reads around 190, heat exchanger around 180, thermostat housing 180, mixing elbow around 160 and the coupler that connects the heat exchanger to the mixing elbow always reads the highest, around 210 or so.
When I push the boat into head seas or a strong current, all the numbers go up a little but the coupler that connects the mixing elboow to the heat exchanger goes up a lot, approaching 300 degrees. The mixing elbow is stainless and this coupler appears to be cast iron. Why so hot? Is that an acceptable temp?

 

[Maine Sail]

I use a laser heat gun to monitor various spots on my diesel engine. At cruise rpms, oil filter reads around 190, heat exchanger around 180, thermostat housing 180, mixing elbow around 160 and the coupler that connects the heat exchanger to the mixing elbow always reads the highest, around 210 or so.
When I push the boat into head seas or a strong current, all the numbers go up a little but the coupler that connects the mixing elboow to the heat exchanger goes up a lot, approaching 300 degrees. The mixing elbow is stainless and this coupler appears to be cast iron. Why so hot? Is that an acceptable temp?

That is the exhaust gas temp before the exhaust water injection point and after the manifold. The cooling jacket in the manifold (depending upon the engine) helps keep the manifold temps down and helps keep it cool. 300F is not an outrageous number for the area between injection and after manifold.. On a car or diesel pick up truck it would be higher measured that close to the engine......

It may or may not be indicative of an exhaust elbow beginning to plug but you'd need to start with a new elbow to get a baseline temp from which to compare numbers...

 

[Bill Roosa]

Laser heat gun?
Perhaps the laser is heating the manifold up due to its high specific absorbance at the frequency of the laser beam. ;-)
or
It could be that there is 2000 deg F exhaust gas in the exhaust manifold.

I'm thinking the latter is more likely though