Engine Oil level too high

[RSB333]

Yesterday I checked the engine oil level in my 1984 Universal M-25 after about 15 hours of motoring. The level was well above the "full" mark, and was quite black. I'm wondering if this is an indication of piston ring "blow-by".
Question: can an engine oil analysis determine whether or not there is a problem? I have not noticed any decline in performance and there's no noticeable change in the engine's exhaust.
RSB333

[cal40john]

Previous thread with most of the possibilities -

http://www.cruisersforum.com/forums/...ng-127757.html

[Wotname]

I'll leave the question of what an analysis of the engine oil can achieve to others however my first thought is diesel contamination.

Possible sources of fuel entering the sump are a faulty lift pump or faulty seals in the injection pump.

Does the oil appear to be thinned or have any other sign of fuel init?

[Wotname]

Originally Posted by cal40john

Previous thread with most of the possibilities -

http://www.cruisersforum.com/forums/...ng-127757.html

Good link

[jlundbe]

I didn't read the link but know your problem may be caused by a faulty injector

[RLaird]

Just had the same issue arise after a long motor sailing voyage. Oil was thinned but not milky.
Found one very wet injector.
Surprised that oil did not smell like fuel but that’s what caused the dilution.

[RSB333]

Thanks for good responses. No mechanical lift pump on this engine, so I now suspect the seal on the injector pump. Am also curious about how a faulty injector could get fuel into the crankcase oil.
RSB333

[a64pilot]

Originally Posted by RSB333

Thanks for good responses. No mechanical lift pump on this engine, so I now suspect the seal on the injector pump. Am also curious about how a faulty injector could get fuel into the crankcase oil.
RSB333

By literally flooding the cylinder, gases blow by rings and liquid fuel will too.
Believe it or not but it’s not uncommon at all for bigger modern four stroke outboards to “make oil” as they call it when used extensively for trolling.

[Catboat Willy]

Hold on just a minute !
We had this problem with out M-35 which is essentially the same engine as the M-25 with an extra cylinder.
Your problem is a common one.
First, be sure you are checking the oil in the correct manner.
The oil dip stick has a rubber seal around it and causes a vacuum around the dip stick. You must break that vacuum in order to obtain a correct reading.

Much like putting you finger over a straw end when the straw is in a glass of water, the vacuum in the straw will hold the water in the straw until the vacuum is released. This is what is giving you an erroneous reading, usually too high.

Here's the way to do it;
Remove the dip stick from the engine at the end of the day. This will give any residual oil in the dip stick tube time to settle back down to the oil pan. i.e overnight.
Next morning, put the clean dip stick in the engine and measure the oil. You will then have the correct reading.
And use a good oil filter, WIX or a K&N for a few changes and you'll find your oil will start to clean up.
Do this before getting too involved as it's a common problem.

[Capn Jimbo]

Originally Posted by Catboat Willy

Hold on just a minute !
We had this problem with out M-35 which is essentially the same engine as the M-25 with an extra cylinder.
Your problem is a common one.
First, be sure you are checking the oil in the correct manner.
The oil dip stick has a rubber seal around it and causes a vacuum around the dip stick. You must break that vacuum in order to obtain a correct reading.

Much like putting you finger over a straw end when the straw is in a glass of water, the vacuum in the straw will hold the water in the straw until the vacuum is released. This is what is giving you an erroneous reading, usually too high.

Here's the way to do it;
Remove the dip stick from the engine at the end of the day. This will give any residual oil in the dip stick tube time to settle back down to the oil pan. i.e overnight.
Next morning, put the clean dip stick in the engine and measure the oil. You will then have the correct reading.
And use a good oil filter, WIX or a K&N for a few changes and you'll find your oil will start to clean up.
Do this before getting too involved as it's a common problem.

Excellent! A great example and answer and sure sounds like a good one. Thanks.

[Macsea]

You may have a faulty seal in the sea water pump, allowing water into the sump pushing up the oil level, check the pump for any signs of dripping water indicating a worn lip seal, drain the oil out, check for water and refill with new oil to correct level plus new filter, you should do this asap as water in the sump can kill your engine, if this isn't the problem it has not cost you much and you have changed the oil which probably needed doing anyway.