very cool carb and intake manifold causing moisture

[bottomfish]

I have a 1995 Johnson J25REOR that after a few minutes of running,moisture builds up on the outside of the intake manifold and carburetor and inside the carburetor horn causing white sludge, eventually stalling out at idle. Starts up after 4 pulls, runs for a minute, spits ,cuts off .Cleaned out fuel tank,new gas same issue. Thinking it could be head gasket, did a compression test which was 100psi + on both cylinders. Any ideas?

 

[OhioRiverFloater]

Don't use alcohol gas. The alcohol is what is cooling the metal more than it supposed to be. Alcohol when it absorbs the water turns white & gets thick. I use to use 100% alcohol in a racing go cart. If it wasn't drained after every race the moisture would turn everything in the tank to a white goo. On this go cart some nights racing it the intake manifold would be solid ice after a good run if we had the jets turned up.

 

[Chris1956]

If you are running E15, I doubt alcohol cooling is your issue. I am not familiar with your motor, but I would be looking for water leaks into the crankcase. The likely culprits are head gasket, or cracks in the water jacket.

 

[racerone]

Nope ----It is the principle of refrigeration.----A liquid ( gasoline ) vaporizing needs HEAT.-----It gets that heat from the carburetor and intake manifold.-----That is why they cool down.-----No cooling water near the intake manifold.---Not caused by a blown head gasket.

 

[Chris1956]

Racer, I have never see white sludge in the intake manifold of any motor. Under your statement that would be common.

I presume the white sludge is fuel mixed with water. Water can and does get into the crankcase from leaks or cracks.

 

[bottomfish]

Thank you.. I haven't had any trouble with gas before. I did read that are putting a lot more ethanol in the gasoline. I will start with non ethanol and re post result.

 

[tphoyt]

I see this happen on cool foggy mornings and days with very high humidity.

 

[flashback]

I had a motorcycle that came with a carb heater just for that reason. Your carb is probably icing up.

 

[racerone]

Some folks are challenged by simple concepts , in my opinion !!

 

[Chris1956]

Racer, I think you are wrong. Lets see what the Op comes up with.

 

[racerone]

An evaporating liquid needs HEAT.-----Therefor the manifold cools down.-----There is no cooling water near the intake manifold !!

 

[Chris1956]

I have seen water in the crankcase of an Evinrude V4. It was not caused by condensation. It was caused by some sort of leak. As a rule Carbs get real warm after running a bit, hence no condensation there. Vapor lock is more common. Airplanes (because of the altitude) are an exception.

The heat absorption of gasoline is real, however I really think it is so much less than the heat of the motor (connected to the intake manifold), that it makes no difference.

 

[flashback]

If the ambient temperature was around 75f and humidity was high it's quite possible you experienced icing. It's common in air cooled engines but can occur in any naturally aspirated motor..

 

[bottomfish]

Update. I drained the gas tank and filled it with non-ethanol gas. Ran good in the driveway and it did not stall. Still some moisture but not as bad. It's been real hot and humid here in SC for sure. I'm hoping all it was is fuel and humidity. I will know Sunday and give an update.

 

[flashback]

The straight gas will help a lot, temps can drop as much as 70f degrees in the venturi where the fuel is mixed with air, add a bit of alcohol and it can get even colder so even if ambient temperature is 100f you can still get icing.

 

[racerone]

Carburetors cool down when running.----Liquid fuel needs heat to vaporize !!

 

[flashback]

Carburetors cool down when running.----Liquid fuel needs heat to vaporize !!

Absolutely, that's why most air cooled piston driven planes have carb heaters otherwise the carb gets choked down with ice and the engine stalls.

 

[ct1762@gmail.com]

Absolutely, that's why most air cooled piston driven planes have carb heaters otherwise the carb gets choked down with ice and the engine stalls.

but an aircraft experiences extreme temp differences. much more than a motor at sea level. ive never heard of an outboard carb icing over ever, but im sure its possible in some weird situation. id think the heat from the motor under the cowling would make this impossible, however.

 

[dingbat]

but an aircraft experiences extreme temp differences. much more than a motor at sea level. ive never heard of an outboard carb icing over ever, but im sure its possible in some weird situation. id think the heat from the motor under the cowling would make this impossible, however.

Carburetor icing is caused by the temperature drop in the carburetor, as an effect of fuel vaporization, and the temperature drop associated with the pressure drop in the Venturi.

The Venturi effect can drop the ambient air temperature by 70 absolute degrees F

 

[bottomfish]

Update. Running the marine gas made a difference for sure. Doesn’t stall at idle. It doesn’t seem to have the rpm’s and has a slight bump at full throttle. I’m gonna rebuild the carburetor and figure out how to check the timing. It’s a 1995 with a lot of hours and original parts. Any thoughts of what to look for as far as timing?