CUMMINS 6BT5.9M HIGH WATER TEMP

[ONTARGET]

I have twin 6bt5.9m motors in a 27 foot boat. one motor runs at normal temp the other runs hotter and will set the alarms off when i run over 2200 rpms. i changed the stat and the heat exchanger is fine.there no blockage in the raw water system , any suggestions.

[Still Running]

I would start with checking the engine water pump.

[Hunter 2]

 .fresh water pump impeller. Also when was the last time you checked the raw water pump impeller?  Easy fix

[BigAl13]

  Just 1 broken off lobe on it can cause an over heat

[Still Running]

Or the impeller slipping on the shaft. I think a 5.9 has a belt driven water pump, could be a loose belt.

[Andys Delight]

Or the impeller slipping on the shaft. I think a 5.9 has a belt driven water pump, could be a loose belt.

Rick knows what he speaks.  Just because there's no blockage in the raw water system doesn't mean the pressure is up high enough.  Check the impeller.

[ONTARGET]

Let me give you all a few more details about this problem motor. I recently changed the impeller , The raw water pump is gear driven. The fresh water system is belt driven and i also recently changed the fan belt. i also checked the raw water line before and after the pump for impeller pcs. The heat exchanger is clear as well.

[Still Running]

I take by you saying the heat exchanger is clear, you mean the raw water flows thru with no problem Right?

If so is the coolant flowing thru the exchanger.? Are the temps of the water in and water out on the engine close to the same?

Your lucky, you have two of the same on the boat. Compare the in and out from one engine to the other. Put a load on the engine as see what happens.
Diesels don't heat up very fast, so tie the boat to the dock, put it gear a little and see what kind of temps you have between the two.

Get something like this.

[BigAl13]

if your sure that your getting coolent flowing do what rick said shoot both engines at all the same spots and should be a dead give away. 5 degrees difference between the 2 is probably normal but if the one motor is running as hot as you say it is you should see a big difference also Im assuming you have two temp gauges. swap the wires from one to the other see if the same engine is still hot

[ONTARGET]

What should be a normal variance between the two motors be ?

[Still Running]

  they should be close. I wouldn't loose sleep over 5 - 10 . How hot dose it get, over 210?

[BigAl13]

there is really no set difference its just that even though there the same motor theyll mever run exactly identical just a little turn on the fuel air mux could cause a little temp change. Like Rick said anything more than ten degree difference would be suspect

[Still Running]

Also like Al said, is the gauge right? Good place to start.