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Monsoon 409 Temp Question


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My new LXR is equipped with the Monsoon 409 6.0 liter built by PCM. During my prop testing the other day I noticed the temp varying from a low of 140 to a high of 168.

These temp swings occurred randomly while I was out running the boat with the higher temps right after a WOT run, however, they’d drop into the 140s after idling around for awhile. The lake water was 55F.

Is this normal for a 409? 

The boat is a 2015 with only 90 hours. Should I consider changing the thermostat?

Any idea where I could get a shop manual for this motor?

My only point of reference was my old Merc Black Scorpion which held rock steady at 160F.

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formulaben

Overheating at idle tends to be impeller, impeller face plate leak, or thermostat. 

Overheating at speed points to the circulation pump or obstruction in the system.  I'd inspect trans cooler, raw water strainer (if installed) and then circ pump.

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4 hours ago, formulaben said:

Overheating at idle tends to be impeller, impeller face plate leak, or thermostat. 

Overheating at speed points to the circulation pump or obstruction in the system.  I'd inspect trans cooler, raw water strainer (if installed) and then circ pump.

It doesn’t appear to be overheating as I believe the stock thermostat is set to 170 F. 
 

Just concerned it may be running too cool.

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is your 6L closed cooled ?  if so my closed cooled LS1 runs around 170-175 - I believe this is due to the heat exchanger.   

Edited by SkiPablo
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