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I have a 2002 boat with twin Cummins 6BTA 330 engines. Both engines have the SMX water pumps with about 20 hours on them. The engines run at 180 – 185 temp and both engines are within 1 degree of each other. The factory props were 22×22 but i had the pitch lowered to 20×22 and the engines will run up to 2900 RPM at WOT. I usually run them at 2000 RPM for most of my boating.
I want the engines to run cooler so I installed the SMX 160 degree Thermostats on both engines with new antifreeze. I took the boat out after the installation on 60 degree day and both engines still run at 180 -185 temps. I have taken the aftercoolers apart and cleaned them, taken the end caps off the heat exchanges and cleaned them also but this seems to make no difference.
I was hoping the 160 degree thermostats would make a difference in operating temperatures but so far they do not.
I feel like there must be something else I’m missing that needs to be completed. Any ideas and help would be appreciated.
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Vessel Name: Tenacious
Engines: 6BTA 5.9 330's - "Seaboard Style"
Location: Long Island, NY
Country: USA
Like Clark stated, there are other factors that effect running temps. As to the burping of air I mentioned, here’s two prior posts:
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At the dock , COLD, take the cap off the heat exchanger. Lower the coolant level by about 2 to 3″. If air is still trapped the burp can blow coolant all over you and the E.R. thus the lowering.
Start the engine and cover the filler neck with a heavy rag to hopefully limit blowback.
Let it warm for a few minutes, then bump the revs to about 1,000. Let run a few more minutes and then raise the revs again to about 1500.
THe higher revs will heat the engine faster and the higher temp will expand any trapped air but the higher revs will have far more push to move those bubbles to the exchanger so they can exit.
Part of this heating is to get the stats to open and release any air.
As far as the final running temp of the engine is concerned that has a LOT to do with the water temps you are running in. As the stats open at 160 or thereabouts if the seawater is warm enough the engine temp will rise to whatever temp the seawater can cool the engine to. Just having cooler starts does not guarantee a lower temp. if the seawater is warm enough to cause the higher temp.
Since you were seeing 180 before then the older stats likely just barely opened whereas the 160 are opened much more.
Of course the other part of the equation of the final cooling temp is what condition is your cooling system in. There is far more to this system than just stats. and the raw water pump.
See my tome below.
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