Nautique 200 ZR409 6.0 overheat issue - Part 2

[jr]

Having overheating problems with a 6.0L.    Was reading through old threads and came across this one that mentions on the ZR409's you are NOT supposed to have a thermostat in the "traditional" position.  

 

Are you supposed to have a thermostat in the housing on the front of the engine just behind drivers seat?

 

from @Kelvin "I have the same boat as you with a similar history. First off, I hope you didn't install a thermostat in the traditional position when you realized one wasn't there. The thermostat on that engine is back near the heat exchanger.

 

https://www.ballofspray.com/forum#/discussion/15876/2011-nautique-200-zr409-6-0-overheat-issue

 

We blew a rod last year, installed a new crate engine and after getting everything attached and hooked up, the engine was running up to 200 degrees after 4-5 minutes.    Pulled out the thermostat and boat ran ~160 all summer.  Figured we would deal with it in the fall and try a new thermostat.  Now it is fall and with the cooler water temps, we put a new thermostat in and boat runs up to 200 again.

 

Has new impeller and we bled out the air as best we could.   May try @Jody_Seal trick of tilting the boat up on the trailer to get the air to burp out.    

 

But if indeed you don't need a thermostat at the front of the engine, that would explain it.

 

Thanks,

Joel

[unksskis]

Did you recently replace coolant when this occurred?

[jr]

Ran water all summer. Put in 50/50 water & coolant when we put the thermostat in.

[DanE]

@JoelR Thermostat is located in the heat exchanger or near it if it's fresh water cooled.

[JackQ]

I have an older 5.7 Excalibur, where the thermostat is located in a hose fitting adjacent to the heat exchanger. as DanE posted your should be in or near the heat exchanger not on the engine. Check the schematic from Pleasure Craft to verify. You should have thermostat installed and typicality should be 180 degrees not the 145 for raw water engines (to reduce corrosion ), running at 180 is more efficient and less wear.

[behindpropellers]

This engine runs a split system. The raw water has an intercooler (which cools the antifreeze),the oil cooler, and tranny cooler. The raw water also has a thermostat which forces the cats to run warmer (located in the rear/top of the engine). The closed system also has a location for a thermostat (which had one before) in the front of the engine by the "U" which is tee'd off to the heater.

 

Without the thermostat in place the engine runs 120-130.

 

Tim

[unksskis]

To answer your question, yes, the thermostat is on the front of the engine on the drivers side, basically below your coolant reservoir.

[jr]

Comical ending to my story. Spend the better part of the afternoon messing around with the cooling system. Then gave up, decided to pull the thermostat so we could ski. After pulling the thermostat housing, started to wonder if we had it in backwards. Flipped it around and put it back together. Worked like a charm. Steady 175 degrees.

 

We did get much better at bleeding the system. For us the best way we found was to take the heater hose off of the T on top of the heat exchange, attach it to a pump garden spray pump and push the coolant through with pressure.

[skiinxs]

Something else to watch for is to make sure the screen in the inline thermostat housing on top of the engine close to the heat exchanger is clean. That screen will eventually clog if not cleaned occasionally. My suggestion is to remove it and throw it away. They quit putting the screen there in the later years.

[RAWSki]

@skiinxs thanks for the tip about the screen. Will check that when we pull ours in a few weeks.

Does anyone know why PCM stopped producing the partial or semi-closed cooling system on the 6L? It's really convenient for those of us in freezing climates.

[DW]

@skiinxs - do you know what year the screen was eliminated?

[skiinxs]

@DW Not sure, cant really remember which one didn't have it, I think it was '16 or '17.

[Alberto Soares]

2010 200 6.0 - 1.700 hrs - Great info on both discussions, part 1 and 2, thank you all.

 

After changing the impeller due to an overheat (my fault - impeller had 300 hrs), the temperature kept raising to 200, so I took the air out of the system as @Jody_Seal instructions and the temperature is now back to 175.

 

One question - when purging the air out of the antifreeze plastic recipient I noticed that at idle (650 rpm) the antifreeze does not go in, I need to raise the RPMs to 800 to make it flow. Could the screen @skiinxs mentioned cause this, I have not checked it yet.

[Jody_Seal]

Was this service update performed?

 

 

[Alberto Soares]

 

Mine is pre CAT

[Jody_Seal]

@Alberto Soares

Ok no screen then LOL!!

If it runs 175* then time to ski! just monitor the coolant level..

[Alberto Soares]

Thank you @Jody_Seal !!!