Water (steam) coming from crankcase vent hose

[ReefRaider]

350 Mercruiser 5.7

So I admittingly got lazy (never again!) and didn't store my boat last winter as well as I should have (1/2 tank of gas, minimal stabil). So I'm pretty much running for the first time in awhile, and I'm getting steam, definitally moisture, blowing out my crankcase vents into the spark arrestor. Please correct my assumptions here.....

No sign of water in oil, engine runs / sounds fine so I assume I have some condensation from somewhere that is "blowing off". I assume this is no big deal as long as assumption 1 is correct. Hopefully with a little more running I'll see it go away. Of course moisture in the fuel tank is different than from than in the engine...so could moisture in the fuel end up as steam at the vents? Or although no sign of water in the oil, maybe I have some from condensation there also. And here's my main question.....the "steam" is coming out of the vents and being sucked right back into the carb through the vent hose attached at the spark arrestor (right?). Should I disconnect the hoses, even if just temporarily, from the spark arrestor to let the steam out away from the carb? Would this hurt anything / be a safety concern?
Thanks in advance,

 

[northernmerc]

Re: Water (steam) coming from crankcase vent hose

Are you sure it's steam, as in vaporized water? If so, it likely is coming from inside the motor. You may have water in the oil from sitting over the winter. Water is heavier than oil and settles out at the bottom of the oil pan, so you would not see it just by checking the oil. Once you start the engine, it all mixes together. Worst case scenario, you may have a blown head gasket or a cracked block.

I can't see that the vapor could come from the gas supply. If it was water in the gas, it would just go into the carburetor along with the gas.

If it is an oily vapor, it could be blowby. A little might be considered normal, but a large amount means a worn engine - possibly worn rings.

As you say, let's hope that it clears up with a little more running.

 

[ReefRaider]

Re: Water (steam) coming from crankcase vent hose

Yes, it's water. Small droplets form there at the end of the hose. Absolutely no oil. I'm confident I have no major water intrusion (blown gasket, cracked block, etc.) and am dealing with condensation. I guess it is possible I could have "minor" water intrusion, I guess time will tell on that one.

But I likely do have some condensation in the engine, and assumed that was probably what was happening (as you said), was just looking for a second opinion.

I'm pretty sure I have (had) water in the fuel, have addressed that, just wasn't sure if that also could be the source of the "steam".

But again, my main question came from watching the steam leave the end of the vent hose and get sucked right back in into the carb and thus engine. Didn't know if that was "ok", even if temporary. Is it then being pushed out the exhaust (and not continuously being recirculated?)

Also didn't know if a little blow off at times, as described, could even be common or normal, in particular after sitting for months (allowing condensation to form in the engine).

Thanks again,

Are you sure it's steam, as in vaporized water? If so, it likely is coming from inside the motor. You may have water in the oil from sitting over the winter. Water is heavier than oil and settles out at the bottom of the oil pan, so you would not see it just by checking the oil. Once you start the engine, it all mixes together. Worst case scenario, you may have a blown head gasket or a cracked block.

I can't see that the vapor could come from the gas supply. If it was water in the gas, it would just go into the carburetor along with the gas.

If it is an oily vapor, it could be blowby. A little might be considered normal, but a large amount means a worn engine - possibly worn rings.

As you say, let's hope that it clears up with a little more running.

 

[Bondo]

Re: Water (steam) coming from crankcase vent hose

I'm pretty sure I have (had) water in the fuel, have addressed that, just wasn't sure if that also could be the source of the "steam".

Ayuh,... No way in 'ell, water can get from the Fuel, into the base....

Leave the vents alone,+ go Run it up to temp...
The vapor you see just gets sucked in,+ blown out the exhaust...
It'll probably clear up after an hours hard Run...

 

[crazy charlie]

Re: Water (steam) coming from crankcase vent hose

Take a look on the underside of the oil filler cap.See if there is anything in the way of a beige cream or condensation droplets.I had a mercruiser that did what yours is doing and it turned out to be a bad head.Ran fine all the time.Pulled one of the heads and it looked just fine.Had it magnafluxed and there were cracks not visable to the eye until magnufluxed that were around the valve opening.Replaced the head and never saw a trace of it again.Charlie

 

[ReefRaider]

Re: Water (steam) coming from crankcase vent hose

Take a look on the underside of the oil filler cap.See if there is anything in the way of a beige cream or condensation droplets.I had a mercruiser that did what yours is doing and it turned out to be a bad head.Ran fine all the time.Pulled one of the heads and it looked just fine.Had it magnafluxed and there were cracks not visable to the eye until magnufluxed that were around the valve opening.Replaced the head and never saw a trace of it again.Charlie

Thanks, I'll check that also but was wondering.....you said head, as in singular. Did you have steam coming out just the one side? Mine is coming out both.

Thanks Bondo, you answered my main question. That is what I'll do.....just run her as is, watch her, and hope it is something that simple and goes away. If not, keep investigating........

 

[crazy charlie]

Re: Water (steam) coming from crankcase vent hose

It was a few years ago but I think it was from both vents.I only checked the one head.Charlie

 

[Rambocj7]

Re: Water (steam) coming from crankcase vent hose

Did you ever solve this problem? I'm having the same problem too.
Steam coming out of both hoses and no water in oil. I've heard it could be the intake gasket.

I have a 7.4L

Let me know!