QSC Blow by

[Dave Carlson]

I have a boat that had a pre-sale engine survey done and one engine’s crankcase pressure reading was 12 inches of water. This was done with a system similar to Tony’s diagram on this site. This is a strong running engine that does not burn oil or smoke with under 700hrs. Is this reading to be considered bad?
We are waiting for oil sample results and are checking the air sep with no problems found yet.

Thanks
Dave

Topic

[Dave Carlson]

Thanks Tony and Phil, we are waiting for the oil sample reports and another blow by test to complete the sale.
I did tell the buyer about the after coolers.

[Philip]

If the engine starts easy when stone cold, doesn’t smoke on startup or when running, is propped under spec and reaches max rpm when heavily loaded then 99.9% that blow-by test is bogus.

If the engine is operated in salt water and has not been fresh water flushed regularly then your aftercoolers are getting ready for removal and service. Your friend should be aware of that.

Phil

[Tony Athens]

“Scoped”———————–NO.

Just the oil level being too high could easily cause the “high blow-by” and is the most likely cause of the high blow-by that was supposedly measured–Totally Bogus test if the if the oil pan was over filled, even by one quart——-This happens all the time. The “B” series Cummins are really susceptible to to this.

99%+++++, your surveyor has no clue..

Send me the oil sample reports..

Tony

[Dave Carlson]

Tony

Thanks for the response. This is a boat that I own and am selling to a friend of mine. The survey was done by a local diesel mechanic with a long history and good reputation. The airsep was disconnected from the valve cover and a system like yours was installed in the hose. These engines start cold normally without smoke and run through the range without smoke. In the 75 hrs I used the boat last year I only added oil during an oil change.
I had oil samples done in June last year and they came back good. You can understand why I was stunned when the engine surveyor said the test was high on the starboard engine.
If 10 inches of water is OK how bad is 12 inches on this engine? The oil level was too high which was corrected this morning.
The after coolers were removed,cleaned, pressure tested and installed two years ago. I pay attention to the fuel curve and the engine is within spec. The air intake temp is within 10 degrees of sea water temp.
If this engine has problems I certainly don’t want to sell it to a friend without knowing what needs to be done.
Should this engine be scoped?

Thanks

[Tony Athens]

I would not put much credibility in the test if you had the Airsep connected.. Got pics of how the test “apparatus” was connected? Who/how was the test performed?…………… I also do not put much thought into a random oil sample……………On this engine what really matters in a cold start test and and proper internal inspections of the aftercoolers ( means they need to be put on the bench).. Also, lets “see the exhaust risers, etc.

If the engine is really over “blow-by” spec in 700 Hrs, you need to ask why? it was not the 700 hours of wear that did it.

700 hours is nothing–Its “Marine Age” that matters and if the boat has been sitting in salt water for years without proper seawater side maintenance.

Tony.

[Author]

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