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12.06.2021 2:38:32
My Yamaha 8 HT all of a sudden was "making oil" the problem was the thermostat was broken (stuck on open) the engine was not running hot enough causing gas to leak down. [links]
See full version: 4 stroke - Gas in Oil
My Yamaha 8 HT all of a sudden was "making oil" the problem was the thermostat was broken (stuck on open) the engine was not running hot enough causing gas to leak down. [links]
You've got a faulty fuel pump diaphragm. The fuel pump is powered by a push rod from the camshaft, and a rip in the diaphragm will allow fuel into the rocker cover on the cylinder head, where it mixes with the engine oil and returns to the oil sump. I would inspect the fuel pump and repair it before using the outboard again, fuel in the crankcase is just an explosion waiting to happen. Here is the parts diagram for your outboard:
Mercury, Mercruiser, Force, etc. - FUEL PUMP - 115 EFI (4-STROKE)
[links]
Any help PLEASE? Thanks in advance! here
Otherwise, is there ANYTHING I might be missing? I find it hard to believe that I can reach top RPM, no smoke in exhaust, and that much fuel is blowing by the rings due to them not being seated. [links]
I think you're mistaken on both approaches. In the first place I believe the low pressure fuel pump is a cam operated diaphram pump. If the diaphram tears, the fuel goes right to the crankcase. Secondly, compression rings being shot would of course cause crankcase pressures, but should have no correlation to raw fuel entering the crankcase. Srowejr is making way too much oil to be caused by anything other than a direct leak of raw fuel into the crankcase. Raw fuel from somewhere other than the combustion chambers.
I have done the following:
Plugs look really good. I guess. no black soot no overheated ceramic around the electrode. Really clean. I will try running it with the VST vent pipe disconnected and extended like you suggest. Can I do that on the trailer or is it best to do it under load? I tried that for about 10 mins on the trailer and did not get anything through the hose should i run it longer on trailer? [links]
Overfilling your engine with oil is as bad as running low on lubricant. But what if you filled it properly yet over time your dipstick begins to show you have more oil than you started with? Your engine could be “making oil,” mechanic slang for fluid intrusion of the crankcase.
Often, making oil results from gasoline blowing by the piston rings. Excess fuel could be getting into the crankcase due to a leaking carburetor or injector or due to a bad intake manifold. If excess gas is the culprit, you can usually smell it on the dipstick. more
Check your oil regularly. This includes boaters running four-stroke outboards, some of whom still operate in “two-stroke mode” (“tilt-it-down-and-go” ) and don’t check the oil before slipping the lines.
If your vehicle’s engine is running with a stuttering or knocking sound; it is possible that one cylinder is not firing correctly; which leads to gas condensing in the faulty cylinder and draining into your oil pan. Accurately diagnosing this problem, requires some specialized testing equipment and; needs to be done by a trained mechanic. more
However, it is normal for a small amount of gas getting into your oil during normal engine operation.
A badly adjusted carburetor can send too much gas into the carburetor; and the overflow will eventually wash down the cylinder walls and into your oil pan. This also tends to foul the spark plugs. Thus, one way to check for this problem is to pull one of plugs and look for blackening on it. It could have a washed look as well. Cars that are more than ten years old usually have mechanical fuel pumps.
Gas getting into oil becomes a cause for concern when the volume of gas exceeds 2.5 percent. If a large amount of gasoline does get into the engine oil; change the oil immediately upon fixing the problem that has allowed this to happen.