Can I (temporarily) run with open thermostat?

[No Worries]

1984 mercruiser 140 3.0. The stat appears to have failed open and I can't track a new one down today. It typically runs about 140ish degrees and now it's about 110ish degrees, I suppose. Not the most accurate gauge but do these numbers sound about right? Anyhow, I can feel warm water on either side of the stat (holding hoses) long before it should open so i think that's pretty cut and dry. Is there any harm running her today 30 or so degrees cool? Thank you.

 

[Bt Doctur]

not really, a small chance of condensation in the oil but nothing deadly and a bit of poor fuel economy

 

[CamaroMan]

i run without mine and runs great, in socal tho. you dont want to do that in milder to cold climates.

 

[No Worries]

I'm in michigan and it probably won't hit 80 degrees today. I don't like the thought of 110 degree oil so the stat will be replaced tomorrow. Just wanna get through today if possible.

 

[bruceb58]

You can run it for a day or two. You never want to run without one long term even if you do boat in a warm climate. The thermostat on my outboard got stuck and since I don't have a temp gauge, it produced around 8 ounces of water over the summer. Very bad for your engine.

And yes...I am in socal!

 

[fhhuber]

Won't hurt much to run with a stuck OPEN thermostat except the engine may never get up to proper temp. This may cause some excess fuel use and may result in faster than normal wear of some parts (like 5000 mi wear in 1000 mi or similar)

Not something you want to do a long time...

Condensation issues don't really happen while running. Just the heat of a light bulb can prevent condensation issues. In fact, many ships use a light bulb inside 25 ton pieces of equipment to prevent condensation while shut down.
Condensation happens with COLD material in humid environments. It a storage issue.

 

[bruceb58]

Condensation issues don't really happen while running.

Condensation alone is not the issue. A by product of combustion is water vapor which gets into the crankcase and the cold engine can't get rid of it.

 

[fhhuber]

Condensation is not the issue. A by product of combustion is water vapor which gets into the crankcase and the cold engine can't get rid of it.

You obviously don't understand the concept.

MM1 USN Naval Nuclear Power.
Corrosion prevention and thus condensation prevention was rather important.

 

[H20Rat]

You obviously don't understand the concept.

MM1 USN Naval Nuclear Power.
Corrosion prevention and thus condensation prevention was rather important.

So I'm curious, how does an engine rid itself of the byproduct of hydrocarbon combustion when both the oil and water temp are below the boiling point of H20? Again, condensation is not the problem here. Combustion is.

 

[fhhuber]

How does water evaporate from a glass on your kitchen table if its not boiling?

Water temp just has to be above dew point and you get evaporation.
(Actually you get some even when it below dew point)

The combustion gasses have to cool significantly before you get condensation out of them.
And... yes, that is condensation.

You are trying to concern yourself with the least significant issue (if a factor at all) due to running with the thermostat stuck open.
forget it. If you are running with the thermostat stuck open long enough for that to be an issue you deserve the result.

 

[bruceb58]

LOL...combustion gasses do cause water to form in the crankcase...no matter what fhuber thinks. Yes..its the condensation of those combustion...not the condensation of atmospheric gasses. It's the reason outboard people have water in our crankcase from stuck open thermostats. The same can happen with I/O's if you run without a thermostat on the system.

Let me guess..Fhuber has never owned an outboard motor that does not come with a temp gauge! LOL. Water does end up in the crankcase fhuber. Do a search on "making oil".

 

[No Worries]

Lol it's all good fellas, changed the stat out on Wednesday. All is good!