Moisture in engine question

Hi,

This is my first post...I appreciate any help. I am looking at buying a used boat with twin 5.7 Crusaders. It is a 1996 fresh water boat with less than 300 hours. It looks like new. Upon my novice inspection last week, all looked good at first glance and the engines ran smoothly. However, on the starboard engine there were a dozen large drops of moisture accumulating on both oil caps. The dip stick oil looked clean, not milky at all. I cleaned the caps and we took the boat out for 30 minutes. The water was under the caps again. The port engine was fine. Both engines just had very faint steam coming from open caps.

I had a shop go inspect the engines. All compressions were between 155-164. He said all plugs looked normal. he poked around with a boroscope and all looked normal. The mechanic says he ran it in the slip for 30 minutes and there was no moisture on the caps after. I was not there to witness as I live far away. I asked the mechanic what he makes of all this and his best explanation was that they had a lot of humidity recently from some storms. I asked then why is port side nice and clean under the caps. He had no explanation.

FYI, after the mechanic left, I did have someone go open the caps the next day and there were numerous small drop of water under the cap.

My gut says there is something starting to go wrong with this engine. What are your thoughts? A few people I've talked to have said don't worry; and, others say worry. You advice is greatly appreciated.

Thanks, Jeff

some moisture accumulation is common....is it best to get rid of it by running the engine, under load for a sustained period of time.....

Did you ask the shop to explore the condensation or 'check out the engines'? if he ran it in the slip for 30 minutes, was it just at idle?

are they fresh water cooled?

makomark said:

some moisture accumulation is common....is it best to get rid of it by running the engine, under load for a sustained period of time.....

Did you ask the shop to explore the condensation or 'check out the engines'? if he ran it in the slip for 30 minutes, was it just at idle?

are they fresh water cooled?

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Hello,

Thanks for the reply. I did specifically ask the mechanic to look for the moisture. I am not sure what rpm he ran it at in the slip. I did run it under load for 30 minutes on a sea trial a few days before he arrived. I would think that should have cleared any condensation?

The mechanic did say that the gas smelled old. He suggested that moisture in the gas could end up showing up as condensation on the valve caps. The other engine is fine, but he told me the starboard engine pulls fuel only from the starboard fuel tank and that could explain the difference.

If there was enough water in the fuel to show up as condensation in the valve covers, wouldn't the engine run poorly? It ran fine.

Thanks for your input. Jeff

The engine crankcase breathes with the rise and fall of the barometer pulling in humid air that condenses. If the engines are running good and the oil is not milky yea just take it for a long run and see if the moisture disappears. Sounds like a non issue to me but definately monitor it close. Do you have a fuel filter/water separator for each engine?

It takes more maintenance for engine that sit a long time than if you run them regularly. If it has engines oil coolers plan on replacing them for your piece of mind if the age is unknown?

The PCV system on the Crusader engines of this era have a simple direct connection to the flame arrestor, no PCV valve. So in essence atmospheric moisture can enter the valve cover where the oil cap is located. It turns out the oil was overfilled on this engine which may have contributed to the moisture on the inside of the cap. Upon changing the 14 month old oil on both engines (only 30 hours), small water droplets appeared about the same in both engines' oil caps. A laboratory analysis of the 14 month old oil by Blackstone indicated the engine in almost new condition. "No measurable moisture showed up in this sample". The new owner is enjoying an older boat in pristine condition.

Same issue. 1995 454XL. Less than 100 hrs on rebuilds. Moisture on oil fill caps AND a peanut butter looking substance in hoses that go from valve covers to flame arrester. Called rebuilder, he came out and looked, said it was normal this time of year in NW Florida. I then called a trusted mechanic of mine. He came out and we ran boat at cruise (3200 rpm) for 45 minutes. Boat ran great. Got back to dock and he checked everything. (timming, compressions, plugs, drained a little oil from pan) All looked fine. Said same as rebuilder, normal. soooo..... it is what it is huh??

kevin_z said:

Same issue. 1995 454XL. Less than 100 hrs on rebuilds. Moisture on oil fill caps AND a peanut butter looking substance in hoses that go from valve covers to flame arrester. Called rebuilder, he came out and looked, said it was normal this time of year in NW Florida. I then called a trusted mechanic of mine. He came out and we ran boat at cruise (3200 rpm) for 45 minutes. Boat ran great. Got back to dock and he checked everything. (timming, compressions, plugs, drained a little oil from pan) All looked fine. Said same as rebuilder, normal. soooo..... it is what it is huh??

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Oil does absorb water. This is a good read:https://www.azic.com/moisture-in-oils-the-three-headedbeast/
If the water is not coming from the cooling system, then it's "normal". Not "good" but "normal". Water in oil does no good. if the engine is not run much, it is free to breath in atmospheric water and hang in free suspension. When heated, the water will want to leave. If it looks milky on the dipstick, or there is free water at the bottom of the pan, then its much more likely there is something wrong.
Do a crackle test.

I work as an engineer and develop products for the electrical utility industry. They may have many gallons of free water in the bottom of these very large transformers. We make a breather that dries air, as the transformer breaths in. They help. Your engine is "free breathing". It inhales and exhales as it is run and the oil expands and contracts.
Make no mistake. Free water in oil is not good. But "some" water is oil is not avoidable. I'd say if the engine is run a lot, you should not be seeing ANY milk on the valve cover cap. But, since the engine sits 99.9% of the time, and the crankcase is not sealed, that oil will absorb oil. Boats for sale are usually not run much, they sit and the oil absorbs water.

Ayuh,.... Condensation in the valve covers,.....

Nothin' a good long run won't fix,....

For peace of mind you can send an oil sample to Blackstone labs. On my sample the water percent was 0.0. There was some fuel in the oil (0.5%). Normal is considered less than 3%. So that's a good number too.

was on boat yesterday. (70 degrees outside). opened engine hatch, and the engines were dripping in 'sweat'. I guess there is no way to prevent it. I closed the hatch, fired up both engines and generator, let idle for about 20 minutes (did put a load on genset) and hopefully that dried things up a bit. will check again today, but my home weather station says low humidity now.

I've often wondered why marine engines do not use the same PCV system that is used in Automobiles. There are certainly different operating conditions in marine applications but the automotive systems seem to do a better job at low RPM's and the marine systems seem to be able to handle larger volumes at higher RPM's. Why can't both systems be used together????

bobbyc said:

I've often wondered why marine engines do not use the same PCV system that is used in Automobiles. There are certainly different operating conditions in marine applications but the automotive systems seem to do a better job at low RPM's and the marine systems seem to be able to handle larger volumes at higher RPM's. Why can't both systems be used together????

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PCV is primarily an emissions fix. Since legacy boat motors are not controlled, as such, PCV is not required. so, they don't have it.

I also have this problem, thank you for sharing your thoughts.

This thread was started back in October 2017.
You may want to dust the cobwebs from it.

Yeah dusty thread but for similar concerns see if the engine is coming up to temp, often with raw water cooled engines the stats get sticky and then the engine runs too cold and the condensation may not burn off. If the one that has condensation on the cap runs cold that could be the cause. If they both run at normal temps then I might be more concerned if one has moisture under the cap...