I have a Yanmar 2gm20f recently rebuilt. I am losing about 1/3 cup of oil every few hours of operation. No leaks, and no smoke, except sometimes at start. Any ideas, what weight oil should I use. I've been using 10 40. The boat is in San Carlos, Mexico. so a good mechanic is impossible to find and I'm trying to do fix myself. Any ideas would be very much appreciated. Thanks
Losing oil
- Thread starter swank
- Start date
Did the enhanced consumption occur after you let the boat set idle for a period of time?
Was this apparently excess consumption rate one that you have actually documented in the past?
If so, how long a time have you been keeping track?
If this was a sudden onset then did this increased consumption rate occur after an oil change?
If so, how long a time did it persist after you added oil? Does this persist if you use the motor daily - for example when you use the motor more than three successive days?
Does this consumption rate reduce if you use the motor daily - say over 3 - 5 days?
Charles
Was this apparently excess consumption rate one that you have actually documented in the past?
If so, how long a time have you been keeping track?
If this was a sudden onset then did this increased consumption rate occur after an oil change?
If so, how long a time did it persist after you added oil? Does this persist if you use the motor daily - for example when you use the motor more than three successive days?
Does this consumption rate reduce if you use the motor daily - say over 3 - 5 days?
Charles
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you said it was just rebuilt did they hone the old liners or replace them...also have you broken in the overhaul yet this is a symptom of improper break in or not honing the liners and your rings may not be seated properly hope i am wrong but you need to check this out and be sure they are seated
I would use a 15-40 but the difference should not account for the loss of 1/3 cup of oil every few hours. Go ahead and perform a simple test; start the engine and get it to normal operating temperature and then remove the oil fill cap and hover the palm of your hand over the opening. You should feel if any a gentle flow of air coming out of the engine but if you feel a strong flow which increases with engine RPM you would likely have engine compression escaping past the piston rings and out the open filler opening. This would usually mean that the piston rings are worn or after a rebuild that they were not properly installed. As a temporary measure you could use a thicker oil like a 20-50 to reduce blowby and boost compression. For a better responses you would need to clarify in more detail the extent of the rebuild and how it was performed. Another way of loosing oil is through worn valve seals but in both instances the oil is driven into the cylinder and burned with the fuel. If the loss of oil is large enough there should be signs of smoke. It might also be useful to have a more precise approximation of the number of hours the engine is ran to produce the loss of 1/3 cup of oil.
also check your antifreeze expansion tank. Could be oil leaking into the coolant
or
could be oil leaking into the raw water through a cracked head which may or may not produce smoke but would certianly coat the exhaust with oil and leave an oil sheen on the water.
or
could be oil leaking into the raw water through a cracked head which may or may not produce smoke but would certianly coat the exhaust with oil and leave an oil sheen on the water.
a little more information could be helpful to give you ideas in an attempt to help you diagnose the problem....
how long have you owned the boat?
does this happen right after an oil change, or all the time?
does it happen if the engine is at slow idle or only when at a higher rpm?
does the oil consumption continue until its way low on the dipstick, or does it seem to stop after running it awhile?
is the engine installed tipped forwards a little, or is it level?
some installation positions cause the oil level on the dipstick to read incorrectly, and nearly always if the dipstick has not been calibrated correctly for the installation position.... if this is what is happening, the oil level you are trying to maintain may be a bit too high, and it would be normal for the oil to be splashed towards the crankcase vent tube and put thru the engine and out thru the exhaust until the correct level is reached.
OR... if your engine is equipped with an oil cooler, the cooler or its seals could be damaged and allowing the oil to go directly into the cooling water stream
but no matter the reason, if the oil disappears and it isnt leaking into the bilge, its only other exit is thru the exhaust.. even if you cant see it.
how long have you owned the boat?
does this happen right after an oil change, or all the time?
does it happen if the engine is at slow idle or only when at a higher rpm?
does the oil consumption continue until its way low on the dipstick, or does it seem to stop after running it awhile?
is the engine installed tipped forwards a little, or is it level?
some installation positions cause the oil level on the dipstick to read incorrectly, and nearly always if the dipstick has not been calibrated correctly for the installation position.... if this is what is happening, the oil level you are trying to maintain may be a bit too high, and it would be normal for the oil to be splashed towards the crankcase vent tube and put thru the engine and out thru the exhaust until the correct level is reached.
OR... if your engine is equipped with an oil cooler, the cooler or its seals could be damaged and allowing the oil to go directly into the cooling water stream
but no matter the reason, if the oil disappears and it isnt leaking into the bilge, its only other exit is thru the exhaust.. even if you cant see it.