View Full Version : Crankcase overfull

11-27-2009, 11:17 AM
"In August, on a Gulf of Maine transit to Nova Scotia, running @ 2800 RPM, we had knocking & blue/white smoke in a couple of incidents that were first suspected of air in the lines. We tightened up the fuel lines, replaced some banjo washers, and had repeat incidents on the same and subsequent days. First time was after running ~2 hours. Then subsequent was ~an hour later. If we ran at 2200 on the level it was OK. Motorsailing @ 2100 heeled a little in 5k breeze would knock & smoke.

Later investigation found the crankcase with an extra 1.25 qts of oil in a 2.75 qt. capacity which was pulled out ounce by ounce with a turkey basting syringe from a hardware store. The symptoms fit with Calder's troubleshooting guide as an overfull crankcase. The balance of the trip proceeded holding the oil level. Looking at last year's yard bill, they had put in a gallon instead of 2.75 qts., so I'm pretty confident that it was not fuel washdown.

So, a couple of questions.
What was happening? I can see from the engine crossection that this amount of overfill would bring the level up, probably, to the bottom of the pistons. Most likely there was excess pressure building in the crankcase that then what? Forced oil up past the rings? Or just the backpressure under the pistons?
Damage likely? We ran back across the Gulf 2 weeks later on an unfortunately windless day/night @ 2800 for 21 hours purring like a kitten (knock on wood). Oil analysis came back good and close to values from two years ago."

11-27-2009, 06:31 PM
You have a stroke of good luck. What is the level in the gear box? Make sure level is correct and monitor your running time. Check for leaks The lube oil and fluids should always be checked before start up. A good habit to get into. What model is the engine?

11-27-2009, 08:23 PM
"Yanmar 3GMF 1985. The dipstick is a little deceiving. It did appear overfull, by maybe 1/8" and so I did not pay it any mind. A mechanic that I had double check our fuel line work in Shelburne, our clear in port, said it looked a little overfull but was not too concerned. Evidently the dipstick does not register any more above ~1/8".
Gearbox level was just right before trip and at the one point during that I checked."

11-29-2009, 08:50 AM
"A couple thoughts on oil levels,
No need to play guessing games with your dipstick,If you are getting ready for a delivery,Change the oil beforehand,Put in the Manuf.suggested amount of oil.Check dipstick accuracy,Then you have your standard to go by.
The delivery crew should be familiar with all the fluids and conditions of fuel delivery and filtering,so you don't have to battle the plugged Racors midstream. Been there,done that... Good luck, Fair winds. JDhttp://www.marineengine.com/discus/clipart/thumbs_up.gif"