350 Verado - coolant temps fluctuating

[SuperDave20]

I have a 350 Verado with less than 100 hours and the coolant temps are fluctuating from 140-168 degrees. It doesn’t do it on the initial start up. I can make two or three fishing stops then it will do it. Eventually it finally settles out to about 143 degrees or so. It will take about 10 mins of running before it will level out.

Anyone seen this condtion? Running a Merc monitor so that’s how I’m getting my readings.

2B365763

[Jig_Man]

Mine seem to go up and down all the time. It varies much more than my old Optimax did.

[Jasonrs]

My 200 4cylinder model is similar, im gonna change my tstat in spring and see if it stops doing it. Have been told its normal, but pretty sure it started halfway through the season.

[SuperDave20]

Mine didn’t do this at first either but has done it the past 3 fishing trips. Water temps were around 62 degrees.

Also so it does not do this when on the water hose at the house.

[bloodman]

Have you pulled the thermostat and inspected it?

[btsmbass]

On the verados the poppet valve is super sensitive. Your still within range and it's still settling at a good temp. If you run in sketchy water often clean your poppet valve occasionally. If it does this while running but not idling it's almost always the poppet.

[SuperDave20]

Gotcha! Sounds like the poppet valve then. I’ll have to do a quick google on how to clean it haha. I’m new the Verado world.

Thanks for the help guys!

[EuropeanAM]

What you are experiencing is quite common on this engine model. If thermostat and poppet are clean, "motor on" once the engine comes up to temp at idle.