Thermostat too dirty

ZafSC

Seaman Apprentice
Joined
Apr 9, 2023
Messages
45
Hello. I removed the thermostat last fall during winterization, and now I wanted to install the new one, but the hole inside it look extremely dirty. Looks like grease and mud, not exactly sure. I didn't notice it previously, because it was full of water (or antifreeze) previously.
Attached are the pictures. Is there some method to clean it before I install the new thermostat? Or I just ignore it?
Thanks
 

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Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,961
Typical of any raw water cooling system used in fresh water. Knock off the big stuff and use it.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
50,709
use a wire brush to remove the rust flakes, install new thermostat, sleeve, and gasket and go boating.

extremely common on a raw water cooled boat in either fresh or brackish water.
 

ZafSC

Seaman Apprentice
Joined
Apr 9, 2023
Messages
45
Allright, thanks folks. I cleaned it, and tried to re-install the thermostat back to its hole.
But a very strange problem, that beats me out. The white plastic sleeve protrudes out of the metal block, see picture 1 and 2. Aren't they supposed to be completely flat with the metal block?
Even I remove the thermostat picture 7, it still protrudes.
Picture 6 is with gasket on, and still not leveled.
Maybe I am remembering wrong? Should it be like in picture 4? In that case the gasket fits tightly.
Anyway, I ignored the protrusion, and installed it, but no good. The gasket is loose and water is leaking out.
The white sleeve sits on the thermostat nicely. How come it was flat leveled before?
The only solution I can think of cut of the sleeve off around 2 mm, or put 2-3 more gaskets.
Thanks
 

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Fun Times

Moderator
Staff member
Joined
May 16, 2009
Messages
9,187
Nope, you can't put the thermostat in the intake manifold like that as you will have temperature issues of all sorts...It has to go up in the thermostat housing like seen above with the sleeve sitting flusher.... First (on a clean inner base) put the cork gasket inside the housing, then the "too radiator" side of the thermostat rests flat to the cork gasket 'then push in the white sleeve.

Sometimes the sleeve is challenging to get pushed in/down by hand after having dirty housings like you have/had? (Light tapping with a soft hammer might be needed as well)
But I'm thinking either the two housing slots for the sleeve didn't get clean/scraped out enough and holding the sleeve up... 'Or the old sleeve is deformed possibly from removal, and you need a new sleeve Merc part number 8M0214947 which with the troubles you're having, it's probably time to just install new sleeve all together.

Also be sure the old cork gasket came out and again, be sure the base is clean too as it looks built up in the photos above...Let's see the inside of the housing now that you cleaned it up some.

The following top image is the correct orientation, https://www.crowleymarine.com/mercr...ermostat-and-housing-single-and-3-point-drain


Here you can see a slot guide though there should be 2,
1751606506598.png
 

ZafSC

Seaman Apprentice
Joined
Apr 9, 2023
Messages
45
Thank you, after some struggling (install-deinstalled the housing several times), it seems working now on the muffs.
  • I put three layers of gasket to make the plastic sleeve level as the thermostat hole (on the engine block)
  • First I put the direction of the thermostat horizontal (unlike the picture). After running the engine, the gauge has not moved, or moved soo little..(around 120F, the minumum) I can't explain it, but I suspect there was a little slack on thermostat that leaked the water, and that prevented the temp sensor (temp sender says in the manual) fully detecting the temperature.
  • I cannot comprehend how the plastic sleeve does not fully fit into the engine hole. It looks like thermostat can be loose any time. It doesn't lock in at all. Only by using gaskets and glues I can create a real force on the sleeve, so that thermostat does not move at all.
  • I un-installed it, replaced the gaskets (Because you cannot use them more than once, I cut them and shape manually) and change the direction of the thermostat as below, (see it is vertical direction now.)
  • I turn the engine on and the gauge quickly goes to 140. I throttle a bit an it reaches to 160, all ok.
  • Just FYI, when thermostat closed, the water comes from the engine hole and goes into the big hose. When thermostat opens at 160F, the water is additionally routed to the two symmetric hoses.
    • Don't know where all three hoses go to.

1751667349824.png
 

ESGWheel

Senior Chief Petty Officer
Joined
Aug 29, 2015
Messages
711
Danger Will Robinson! We need someone with experience on this system to help the OP further, like @Fun Times

But in the meantime, what you are describing in post 12 can harm your motor. Two things jumped out to me: (1) needing 3 gaskets to make it work and (2) installing the t-stat upside down.

There is something wrong with either the upper housing or the sleeve as highlighted above. With all your time invested it may worth it to get a new upper housing and sleeve if you cannot get the assembly to go together properly. From what I have read, the sleeve holds the t-stat in place against the cork gasket in the upper housing. It also has a particular orientation to allow for the water to flow to the manifolds.

Bottom line: do not continue to cobble this together this way or that. ONLY put it together the way it is designed else you are running an experiment whose outcome will be not good.
 
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