260DA 6.2 overheating

UPDATE...

Yes, she held temperature!! thanks for everyone's help!

Had an awesome weekend! ...Christmas Boat Parade pics coming...
 
Update 1/14/18

welll.. over the holiday she did start to creep up on temp one time.. i slowed off plane and she cools down.. otherwise seemed to hold 158

yesterday i replaced the thermostat housing and sensors.. as you can see the old one was very rough with internal rust stalactites...

its cold here in FL this week so not a boat day... hopefully test next weekend...

 
so couple weekends ago she crept from holding 158 to 171 in a half hour of running on plane.

have installed a 140 thermostat... will see this weekend what she goes up to...

read the 140 could help engine scaling too with our warm gulf waters...
 
Happy Dayz said:
so couple weekends ago she crept from holding 158 to 171 in a half hour of running on plane.

have installed a 140 thermostat... will see this weekend what she goes up to...

read the 140 could help engine scaling too with our warm gulf waters...
Click to expand...


fuel injected engines need to reach around 170*F to run efficiently.....if the coolant temperature sensor does not sense the engine has reached 'normal operating temperature' it will not allow the ECM and other various sensors control the engine at its most efficient level and you will burn more fuel than needed.....

cliff
 
I wouldn't do that either. Run what Merc says to. Nothing wrong with 170, but my 2006 mpi used to run 161*, then creep up after shut down. Creeping while on plane would indicate, to me, more blockage.
 
I hear what you're saying, but I think dropping the t-stat to a lower temp is a bandaid. I'd be a little less concerned if it was an older, carb'd engine... but as mentioned by the guys above, this could lead to other issues.

I didn't read back through the entire thread, but there's a good chance that what you see inside your old t-stat housing is also happening inside the block. Plus, the block's cooling passages could be blocked with sand or silt. I'd suggest a full block flush (a couple of times) and then maybe even run muriatic acid through it.
 
Also keep in mind that the t stat only controls the minimum temp and cannot do anything after that temp is reached.
 
also remember that the t'stat rating is when it 'starts' to open, not the coolant temp it is designed to maintain....

for example a t'stat rated at 160*F will 'start' to open when the coolant temp reaches 160* but it will not be 'fully' open until some point later such as when the coolant temp reaches 170*....that is why a lot of people get confused when they have a 160* t'stat installed in their engine but the temp gauge reads 170*......

cliff
 
Well, somehow my factory installed stats worked differently. 2006 mpi closed cooled, always ran at 161* for years.
Well low n behold when I pulled one and replaced it with the same part it was, in fact a 170*. Go figure....
 
scoflaw said:
Well, somehow my factory installed stats worked differently. 2006 mpi closed cooled, always ran at 161* for years.
Well low n behold when I pulled one and replaced it with the same part it was, in fact a 170*. Go figure....
Click to expand...


yeah I have seen some cases where the temp gauge would read very close to the t'stat rating but in my experience 90% of the time there was usually a several degree difference between the rating and the actual coolant temp.....

cliff
 
this is taken directly from the 'Stant' web site.....

upload_2018-2-6_14-3-53.png
 
I'm giving you real world numbers on an actual boat over a 7 year period without the jiggle.
 
I've found that the Smartcraft equipped engines tend to show around the 161*, whereas the "regular" gauges tend to show more like the 170*. It wouldn't surprise me if there was a slight difference from one t-stat housing design to another, either. Personally, I like the regular gauges as I can see the needle move slightly as the t-stat opens and closes. I've never watched a SC gauge close enough (long enough) - possibly it varies as well? From my experience, though, it tends to hold steady.
 
Well there some good discussions!! thank you all! finally some real info...

and now creating concern to go back to 160...

summary: i have cleaned everything thoroughly, risers and mani 3 yr old and cleaned, new impellar and wear plate, new circulating pump, new thermostat housing thermostat and sensors, hoses flushed, no bravoitus and has the fitting thru hull...

next is the block flush... there is where i see a lot of surface rust

i only get 4-5 psi running 4k rpm

she first would tick up and then ramp up, alarm and even shut off the first time
now ticked up to 171 after 30 min on plane spike to 183 when dropped off plane..

my concern is our water is currently 64 but will go to 86 in summer... my thought was the 140 stat will start more flow sooner through engine, engine would still get to 170 after running if thats all it can maintain???

thanks again for all the responses...! just dont want to hear the wife bitchin this summer
 
Your pressure is low, which would indicate to me you're lacking water volume before the sensor. There's 2 sides to that raw water pump impeller, not familiar with the wear plate but what's on the opposite side of that plate you replaced.
 
The water pressure sensor is BEFORE your block. That means it essentially reads the amount of water coming into the engine (pressure, not flow, but you get the idea). 4-5 psi at 4,000 rpm about a 1/3 of what it should be. The two most common reasons for this is a worn impeller/plate/housing or Bravoitis. How did you verify your engine doesn't have that disease?

It "could" be a faulty sensor, but typically if it's showing a changing reading they're OK. But that doesn't mean that's ALWAYS the case.
 
Isn't that pressure sensor mounted on the steering cooler?

There is a lot of info in these posts, and I think you are very close to a resolution.

Here's a few suggestions:

Step 1:
Remove raw water the discharge from the raw water pump.
Start the engine (after sitting at least 8 hours) and run it at 3,00 rpm VERY Briefly. Just long enough to see what the flow looks like from the pump.

Step 2:
Reconnect the hose, and do the same at the very fist connection AFTER the raw water pressure sensor. Mentally Compare the 2 flow rates.

If there is significantly less flow in step 2, you have some sort of blockage between the raw water pump discharge and the spot disconnected in step 2.

Scoflaw in post #21 mentioned the power steering cooler.

You also stated that when you originally went to install a new impeller, that the current one was in good shape. There is a good possibility that the previous owner replaced it recently, maybe due to an overheating issue. If the impeller broke up, there could be a piece lodged in the system between the raw water pump and the pressure sensor.
 
FYI,
I have a 160 thermostat in my 350 MAG.
Smart craft gauge shows 158-159 degrees all day long, once its warmed up.
 
Did you ever do the raw water pump test I posted about previously?
 
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